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PRINCIPLES 



OF 



CHEMISTRY: 

EMBRACING THE MOST 

RECENT DISCOVERIES IN THE SCIENCE, 

AND THE OUTLINES OF 

ITS APPLICATION TO AGRICULTURE MD THE ARTS. 

DESIGNED FOR THE USE OF COLLEGES AND SCHOOLS. 

A NEW EDITION— ENLARGED AND IMPROVED, 

WITH THREE HUNDRED AND TWENTY-FIVE ILLUSTRATIONS, EXHIBITING 
PARLOR AND LECTURE-ROOM EXPERIMENTS 



BY JOHN A. PORTER, M.A., M.D., 

PSOFKSSOB OF ORGANIC CDEMISTtY IN YALE COLLEGE. 



NEW YORK: 
BARNES & BURR, 51 JOHN STREET. 

1864. 



cS 



*9 






^ 



Entered according to Act of Congress, in the year 1864, by 

A. S. BARNES & BURR, 

In the Clerk's Office of the District Court of the United States, for tho 
Southern District of New York. 



zUU 



Elcctrotyped by Printed by 

Smith «fc McDougal, George W. Wood, 

84 Beekman St. 51 John St 






PREFACE. 



In the revision and enlargement of the " Principles 
of Chemistry," the Author has made it his especial 
care to retain those peculiar features of the work to 
which it owes its distinctive character as a text-book, 
and which have secured for it, among teachers, such 
wide approval. 

Especially designed for beginners in the science, 
whether in schools or colleges, great effort was made 
in the original volume to simplify the study of Chem- 
istry, and to save teachers much explanation which 
would otherwise be required. To this end, the facts 
were more carefully classified than is usual, many de- 
tails of interest only to the professional chemist were 
omitted, great simplicity of statement was uniformly 
observed, and chemical phenomena were described in 
ordinary, as well as in symbolic language. In pursu- 
ance of the same general design, a large number of ex- 
periments were devised, of the utmost simplicity, 
extending over a wide field of the science, and bringing 
the illustration of the subject within the reach of every 



IV PREFACE. 

pupil. A series of new and original designs were also 
introduced, illustrating to the eye the * groupings of 
organic chemistry. All of these characteristic features 
have been retained in the revised edition. 

While a new class of cuts have been introduced, 
illustrative of lecture experiments, and adapting the 
book more completely to college use, all of the more 
simple experiments with the figures describing them, 
have been preserved in the present edition. This 
course has been pursued, first, because of the great 
advantage which it gives to the student, who with 
limited means at his command, still entertains the am- 
bition to become an experimenter, and secondly, be- 
cause the figures referred to, serve, in proportion to 
their simplicity, as object-lessons of the most effective 
character, and take the place of experiments where the 
experiments themselves cannot be performed. This is, 
however, according to the testimony of teachfers, but a 
small part of the end which they serve. The reduction 
of the experiment to its very simplest form is found to 
simplify greatly to the learner the apprehension of the 
subject which it illustrates. 

In pursuance of" the leading object of the re- 
vision, viz., to bring the work up to the present 
condition of the science, considerable portions have 
been entirely rewritten, and every page carefully re- 
vised. 

The Chapter on Animal Chemistry has been so ex- 
panded as to include a presentation of the more inter- 
esting topics in Human Physiology, and will be found 



PREFACE. V 

amply illustrated by cuts introduced for the first time 
in this edition. 

The revision has necessarily resulted in a consider- 
able enlargement of the work, and it will now be found 
to contain quite as extensive a survey of the science of 
Chemistry as can with advantage be pursued in an or- 
dinary college course. 

So large a number of authorities have been consulted 
in the preparation of the new edition, that special ac- 
knowledgment of each cannot be attempted. 

The author would, however, express his especial 
indebtedness to the articles of Professor Graham, on 
" Crystalloid and Colloid Substances, 5 ' and to Professor 

Tvndall's lectures on " Heat considered as a Mode of 

«/ 

Motion." It has not been deemed advisable to modify 
the language employed in the Chapter on Heat, or the 
mode of presenting the subject, in view of the recent 
more perfect development of the dynamical theory. To 
carry out any such purpose consistently, would have 
been impracticable, inasmuch as the new theory has 
not as yet provided itself with an adequate vocab- 
ulary. 

It has been deemed the wiser course to hold strictly 
to the material theory in the description of phenomena, 
and the statement of principles, and to indicate in con- 
nection with each important topic the difference of 
conception which the dynamic theory requires. 

It remains for the author to express his great obliga- 
tions to Dr. M. C. White, of New Haven, and Profes- 
sor Seely, of Middlebury College, for important aid 



VI PREFACE. 

rendered in the revision of this work. He would also 
embrace this opportunity of expressing his acknowledg- 
ments for the favorable reception accorded to former 
editions of the work, and his hope that the effort to 
make the present revised edition still more worthy of 
approval, may not have been altogether unsuccessful. 



JOHN A. PORTER. 



New Haven, Conn., 
Aug., 1st, 1864. 



TABLE OF CONTENTS. 



PART I. 

PHYSICS 



PAGE 

Atoms and Attraction, T 

Three States of Matter ; Contact of Atoms, 10 

Light. — Chemical Action of Light, 11 

Theories of Light, 12 

Laws of Light, 14 

Reflection, 16 

Refraction, 18 

Analysis of Light, 22 

Spectral Analysis, 25 

Heat. — Nature and Sources, 26 

Communication of Heat ; 32 

Changes effected by Heat, 55 

Expansion, 58 

Liquefaction, ?1 

Vaporization, 76 

Boiling, 89 

Mechanical Equivalent of Heat, Ill 

Magnetism and Electricity, 116 

Correlation of Forces, 149 



PART II. 

CHEMICAL PHILOSOPHY. 

Laws of Combination. 

Number of Elements, 151 

Atomic Constitution, 151 



Vlll TABLE OF CONTENTS. 

PAGE 

Explanation of Symbols, 153 

Chemical Equivalents, 15*7 

Properties of Acids and Bases, 160 

Effects of Solution, 161 

Electrical Kelations of Elements, 161 



PART III. 

IINTOIRG^AJNTIC CHEMISTRY, 

Non-Metallic Elements. 

Classification of Elementary Bodies, 163 

Oxygen, 163 

Chlorine, 173 

Iodine, 181 

Bromine, - 184 

Eluorine, 185 

Sulphur, 186 

Nitrogen, 200 

Phosphorus, .212 

Arsenic, 217 

Carbon, 228 

Silicon, . . 244= 

Boron, , 246 

Hydrogen, 241 

Flame, 286 

Incandescence, 294 

Color of Flame ; Spectra of Metals, 296 

Metals. — Physical Properties of Metals, 299 

Classification of Metals, 301 

Class i. — Potassium, &c, 303 

Class ii. — Barium, &c, 310 

Class iil — Aluminum, Manganese, Iron, &Cy .312 

Class iv. — Tin, Antimony, &c, 326 

Class v. — Bismuth, Copper, &c, 331 

Class vi. — Mercury, Silver, Gold, &c, 339 

Salts. — Solution and Crystallization, 362 

Variety of Crystals, 372 



TABLE OF CONTENTS. ix 

PAGE 

Systems of Crystals, 374 

Isomorphism, -. 377 

Oxides, 378 

Chlorides. 390 

Fluorides, 398 

Sulphurets, 398 

Sulphates, 401 

Nitrates, 407 

Carbonates, 411 

Phosphates, 416 

Silicates, 419 

Borates, 427 

Chromates, 428 

Manganates, „ 430 

Photography, 431 



PART IV. 

OIRG^AJSTIC CHEMISTRY. 

General "Views, 441 

Vegetable Chemistry, 460 

Growth of Plants, 460 

"Wood and its Products, 467 

Starch, 487 

Gum, 491 

Sugar, 493 

Alcohol, 497 

Organic Acids, 511 

Organic Bases, 524 

Essential Oils and Resins, 526 

Protein Bodies — Putrefaction, 538 

Permentation — Bread Making, 541 

' Coloring Matters, 548 

Dyeing, 549 

Calico Printing, 552 

Agricultural Chemistry, 554 

Animal Chemistry 564 



X TABLE OF CONTENTS. 

PAGE 

Circulation of Matter, 601 

Appendix, 606 

Smee's Battery, 60? 

Groves' Battery, 607 

Ruhmkorff Coil, 608 

Atomic Theory, 609 

Specific Gravity, 611 

Atomic Heat, 612 

Estimating the Value of Guano, 616 

Physical Tables, 61? 

Linear Expansion of Solids, 61? 

Specific Heat, 61? 

Melting Points of Solids, 61? 

Boiling Points of Liquids, 618 

Composition of Human Blood, 618 

Composition of Cow's Milk, 618 

Proportions of Sanguineous and Respiratory Food, 619 

Amount of Alcohol in Spirituous Liquors,. . » 619 

Solubility of Substances in Water and Acids, 620 

Homologous Series of Organic Acids, 622 

Composition of Ashes and Common Crops, 622 

Index, * . 623 

List of Chemicals and Apparatus, 631 



INTRODUCTION. 



According to the most ancient view of the constitu* 
tion of matter, the earth and all material things are but 
modifications of one and the same original substance. 
Fire, "water, and air, were each in turn asserted to be 
the primitive element, according to the arbitrary con- 
jecture of philosophers who w^ere bold enough to spec- 
ulate upon the subject. At a later date, the views of 
all seemed to be harmonized in ascribing the same dig- 
nity to the three contending elements, and including 
earth among the original varieties of matter. Earth, 
Air, Fire, and Water, were assumed to be the original 
materials out of which all forms of matter are produced. 

Modern chemistry has dethroned each of these ele- 
mental monarchs of the world, and distributed their 
prerogatives among a larger number. Earth, ah*, and 
water, are all excluded from the list of elements, and 
fire appears in the modern view as only the transient 
attendant of chemical combination. 



INTRODUCTION. 



Each one of the acknowledged elements has its own 
specific properties, affinities, and capacity of combina- 
tion. These peculiarities, and all resulting phenomena, 
it is the province of chemistry to investigate and ex- 
plain. Light, heat, and electricity, stand in intimate 
relation to all chemical action, either as cause or effect, 
or unfailing attendant, and are, therefore, briefly con- 
sidered in the earlier part of the present work. 

The study of science has not for its object the mere 
gratification of an idle curiosity. Looking at the sub- 
ject from a material point of view alone, chemistry is 
one of the great agents in the transformation of nature, 
and its subjugation to the wants of man. The earth 
yields her treasure to its skillfully conducted processes, 
and even the trodden clay becomes converted in its 
crucible into shining metal. The arts draw from it, 
with every succeeding year, increased advantage, and 
the condition of mankind is elevated, and the world 
advanced by its progressive triumphs. Agriculture 
also is indebted to its discoveries. It opens to us mines 
of agricultural wealth in what w^ould otherwise have 
passed for worthless refuse. It clothes exhausted fields 
with new fertility, by the addition of some failing con- 
stituent whose absence its subtle processes have de- 
tected. It carefully investigates the laws and condi- 
tions of vegetable growth, by which earth and air are 



INTRODUCTION. 3 

converted into food for man and beast, and thus places 
ns on the highway of sure and rapid improvement. 

These practical results, which are the basis of that 
material prosperity in which taste, and literature, and 
the graces of life find their natural growth, are by no 
means to be disregarded. But this is not all. The 
study of chemical science reveals to the mind a beauty 
and harmony in the material world, to which the unin- 
structed eye is blind. It shows us all of the kingdoms 
of nature contributing to the growth of the tiniest plant, 
and feeding the nascent germ, by the inter-revolution 
of their separate spheres. It shows us how through 
fire, or analogous decay, all forms of life are returned 
again to the kingdoms of nature, from which they were 
derived. "Without encroaching upon the domains of 
the astronomer, it reveals to us still more wonderful 
relations of distant orbs, which affect not only the 
outward sense, but supply the very forces which we 
employ in our contest with the powers of nature. It 
unveils to us a thousand mysteries of cloud and rain, 
of frost and dew, of growth and decay, and unfolds the 
operation of those silent yet irresistible forces which 
are the life of the world we inhabit. 

But the study of nature is worthy of being pursued 
with a still nobler aim. The glory of the Deity shines 
in every crystal and blooms in every flower. Every 



4 INTRODUCTION. 

atom is instinct with a life which the Creator has im- 
parted. The laws that govern the minutest particles, as 
well as the grander revolutions of the heavenly spheres, 
are but the expression of His will. The reverent study 
of nature is therefore a contemplation of Deity. Vague 
and unsatisfactory without the aid of another, and 
written revelation, it unfolds to the mind thus enlight- 
ened, new and exalting evidences of the infinite wis- 
dom and "beneficence of the Creator of the world. 



INTRODUCTORY. 



L The Science of Chemistry is of the widest range. 
Air, Earth, Fire, and Water, all belong to its do- 
main. 

It informs us of the composition of the rocks which 
make up the mass of the Earth, and of the soil which 
forms its surface. It tells us of what Air is made, and 
how it supplies the wants of animal and vegetable life. 
It separates "Water into gases, and reproduces it again 
by uniting them. It informs us of the nature of Eire, 
and of the changes which take place in combustion. 

2. It tells us of what plants are formed, and what 
becomes of them when they decay and disappear. It 
tells us how to produce metals from ores, wines from 
fruit, liquors from grain, and shows us the changes 
which take place in the formation of all these sub- 
stances. Almost all transformations which occur in 
the materials around us — as, for example, of iron into 
rust, of wood or coal into gas, of food into flesh — it 
belongs to Chemistry to describe and explain. 

Questions. — 1. What does Chemistry tell us of earth, air, fire, and 
water ? 2. What of metals, plants, and wines ? 



6 INTRODUCTORY. 

3. As all of tliese changes result from the action of 
the minute particles of matter on each other, it is ne- 
cessary first to consider the subject of Atoms. 

4. As the most of them depend on changes of tem- 
perature, it is necessary, in the first part of the work, 
to consider the laws and effects of Heat. As these 
laws are best understood from their analogy to the 
laws of Light, and as Light has an important influence 
in many chemical processes, a brief chapter on Light 
precedes the chapter on Heat and its various effects. 

5. As many, and perhaps all chemical changes, are 
accompanied by electrical phenomena, it is also impor- 
tant to dwell briefly on the subject of Electricity before 
proceeding to what is more strictly the science of Chem- 
istry. The first part of this work is, therefore, devoted 
to the consideration of these subjects; or, in other 
words, to the Science of Physics. 



3. Why does it treat of atoms ? 5. Why of heat and light ? 5. Why is 
electricity introduced ? 



PART I. 

:p h y s i o s. 



CHAPTER I. 

^.TOMS ^ZSTID ATTRACTION. 

1. Atoms. — All matter is supposed to be composed 
of exceedingly minute spherical or spheroidal particles, 
which are held together by their mutual attraction, 
and are never themselves subdivided. These particles 
are commonly called atoms. There is reason to believe 
that the atoms of different substances differ from each 
other in weight and perhaps in size. The belief that 
they are never subdivided is not based on their extreme 
minuteness, but on other grounds, to be mentioned 
hereafter. 

2. Minuteness of Atoms. — Their minuteness is illus- 
trated by the fact that a single grain of musk will fill a 
room with its fragrant particles for years, without suf- 
fering any considerable loss of weight. The number 
of atoms it gives off during that time is beyond com- 
putation. 



Questions. — 1. Of what is matter composed ? What is said of atoms ? 
. How is the minuteness of atoms shown? 



8 PRINCIPLES OF CHEMISTRY. 

3. Elements. — There are at least sixty different kinds 
of matter. Eacli kind which cannot be separated into 
other kinds is called an elementary substance, or sim- 
ply an element. Iron and carbon or charcoal are 
elements. Iron rust, on the other hand, is a compound. 
There are, of course, as many different kinds of atoms 
as there are of elements. 

4. Cohesion. — The force which binds together atoms 
of the same kind is called the attraction of cohesion, or 
simply cohesion. In the more tenacious substances, 
such as iron or copper, the force of cohesion is immense. 
The strength of a horse is insufficient, for example, to 
break an iron wire one-fourth of an inch in thickness, 
because in every section of the wire the atoms attract 
each other with a superior force. As we may imagine 
innumerable sections in every inch of the wire, we see 
that there is in every inch a force of attraction exerted, 
which in its sum total is inconceivably great. Attrac- 
tion between unlike atoms in contact with each other, 
as between glue and the wood to which it is applied, is 
called adhesion. 

5. Gravitation. — Unlike the force of attraction men- 
tioned in the preceding paragraph, gravitation is an 
attractive force which acts at all distances. The weight 
of all bodies is due to gravitation; one body weighs 
twice or three times as much as another, because it has 
twice or three times the quantity of matter to attract 
and be attracted by the earth. 

3. Define and illustrate an element ? 4. What is cohesion ? Illustrate 
the subject ? What is adhesion ? 5. How does gravitation act ? 



ATOMS AND ATTRACTION. 9 

The attraction of gravitation causes terrestrial bodies 
to fall to the earth, and the same force extending to 
celestial bodies retains the planets in their orbits. 

6. Chemical Attraction, or Affinity. — The force 
which unites unlike atoms to form compounds possessing 
new properties is called chemical attraction, or affinity. 
Thus iron and oxygen unite by chemical attraction to 
form iron rust, a substance different from either. The 
gas chlorine and the metal sodium unite, as will be 
hereafter seen, to form common salt. When substances 
become thus united by chemical affinity, the resulting 
compound is not a mere mixture, with properties of 
both constituents, as when salt and sugar are mixed ; 
it is, on the contrary, a new substance, with properties 
of its own. 

7. Distance of Attraction. — The forces of attrac- 
tion above mentioned, with the exception of gravita- 
tion, act only at immeasurably small distances. The 
attraction of two plates of glass, an inch apart is too 
feeble to be perceptible, and when brought into appar- 
ent contact they exhibit but little cohesive attraction. 
But if two plates of glass, well polished and perfectly 
clean, are pressed together with great force, the atoms 
are brought within the range of cohesive attraction, 
and they unite so firmly that fracture takes place in 
any other direction quite as readily as in the line of 
union. So iron and oxygen will not attract each other 



6. What is chemical attraction or affinity ? 7. Do the forces of cohe- 
sion and chemical affinity act at great distances ? 



10 PRINCIPLES OF CHEMISTRY. 

from a distance, but when brought together, they unite 
in consequence of their chemical attraction. 

8. The three kinds of attraction are perfectly illus- 
trated in a falling drop of water. Affinity holds to- 
gether the atoms of oxygen and hydrogen which make 
up each particle of water. Cohesion unites the parti- 
cles of water thus formed, to make the drop, and grav- 
itation causes the coherent drop to fall. 

9. Three States of Matter. — There are three dis- 
tinct states or conditions of matter — the solid, the liquid, 
and the gaseous. Almost all substances may be made 
to assume each of these states. Thus, a piece of solid 
sulphur, if heated up to a certain point, melts and be- 
comes liquid. If the liquid sulphur be exposed to a 
still higher temperature, it passes off in the form of a 
vapor or gas. 

10. Contact of Atoms. — The atoms of matter are 
not supposed to be in absolute contact in either solids, 
liquids, or gases. This is inferred from the fact that 
all substances may be diminished in bulk by pressure. 
But in solid bodies the attraction of cohesion between 
the atoms is strongest, and they are more nearly and 
firmly bound together. In liquids, cohesion is less 
than in solids, and the atoms are free to roll and glide 
around each other. In gases, cohesion is entirely over- 
come, and but for gravity, the atoms would separate 
themselves indefinitely. 

8. Illustrate the three different kinds of attraction. 9. What are the 
three states of matter ? 10. Are atoms in contact ? What is the cause 
of the difference of cohesion in bodies ? 



LIGHT. 11 

Heat is the main cause of this difference in cohesion. 
This subject will be more fully considered in the chap- 
ter on Heat, or Caloric* 



CHAPTER II. 

11. Light is the Soukce of Yision. — We ascribe the 
phenomena of vision, by which we obtain our principal 
knowledge of the material world, to a mysterious agent 
called light. 

12. Chemical Actiox of Light. — Daguerreotype pic- 
tures are produced by the chemical action of light. So, 
light acts chemically in converting water and the car- 
bonic acid of the air into vegetable matter. The action 
of light in these cases will be explained hereafter. 
The present chapter is devoted to the consideration 
of its nature and more important laws. 

13. Light is without Weight. — While the effects of 



11. To what agent do we ascribe the phenomena of vision? 12. In 
what cases does light act chemically ? 13. Has light weight ? 



* The subject of Crystallization belongs to Physics, and in a strictly scientific 
arrangement, would be considered in this place. The student will find the most con- 
venient illustrations of this subject in the Salts, which are considered later in the 
work, and it has therefore been introduced in the chapter which treats of these com- 
pounds. It is to be borne in mind that what is there said of crystallization, relates 
to other compounds and to elementary substances, as well as to salts. 



12 PRINCIPLES OF CHEMISTRY. 

light, and the laws according to which they take place 
are well understood, philosophers have differed widely 
with respect to its nature. It is, however, agreed that 
light is imponderable, or without weight, this being in- 
ferred from the fact that an illumined object weighs no 
more than the same object when unillumined. 

14. Newton's Theory. — Newton maintained that 
light is a material substance, thinner or more subtle 
than air, or any gas, but composed, like these, of mi- 
nute particles, constantly given off from the sun and 
all luminous objects. He supposed that it is this sub- 
stance passing into the eye that produces the sensation 
of sight, as the fine particles of fragrant matter, passing 
off from flowers, produce the sensation of smell. 

15. Undulatory Theory. — Another view is that a 
very subtle fluid pervades all space, and serves as a 
medium for producing the sensation of light, as the air 
does for producing sound. This view is now generally 
accepted. 

16. When a bell is struck its vibrations are commu- 
nicated to the air, and thence to the ear, producing the 
effect of sound. So, according to the undulatory theory 
of light, vibrations are caused by some means in the 
sun and certain other bodies, which being rapidly trans- 
mitted through the fluid above mentioned, produce, 
when they fall on the eye, the sensation of light. 

17. Existence of the supposed Fluid. — Such a fluid 



14. What was Newton's theory ? How is the sensation of sight pro- 
duced ? 15. What is the other view of the nature of light ? 16. Illus- 
trate this view. 17. How is this fluid known to exist ? 



LIGHT. 13 

as this theory requires is known to exist in the spaces 
between the heavenly bodies, by the influence which it 
exerts on their motions, and is supposed to pervade all 
substances, whether solid, liquid, or gaseous, occupying 
the spaces between their particles. It is called ether, 
but has no relation to the chemical and medicinal liquid 
of the same name. 

18. For the explanation of the leading phenomena of 
light, it matters little which of the views above men- 
tioned is adopted. Thus, in the study of the laws of 
reflection, it matters little whether we regard light as 
a subtle fluid whose particles rebound from polished 
surfaces as a ball does when thrown against a house, 
or whether we suppose it to consist of ethereal vibra- 
tions which take a new direction from impact upon 
certain surfaces, as do the vibrations of the air in the 
case of echoes. 

19. The definitions and laws of light are stated in 
the language of the Newtonian theory, because they 
are thus more easily understood. We employ this lan- 
guage without adopting the theory, just as astronomers 
say that the sun rises and sets, though it is well known 
that the sun is fixed in the heavens, while the earth 
revolves on its axis from west to east once in twenty- 
four hours. 

20. Ray, Pencil, Beam, and Medium, defined. — 
Light moving in a single line is called a ray of light, 

IS. How does either view explain reflection ? 19. Which theory is 
used in stating the laws of light ? Why ? 20. What is a ray of light ? a 
pencil of light ? a beam of light ? a medium ? 



14 



PRINCIPLES OF CHEMISTRY. 



In such rays or lines light is constantly passing off from 
all visible objects. From every part of the book before 
the student, for example, it passes into the eye, enabling 
him to know the nature of the object. If the book is 
taken into a dark room it is no longer visible, because 
it obtains no light which it may afterward reflect to 
the eye. A collection of rays proceeding from a point 
is called a pencil of light. A collection of rays moving 
in lines parallel to each other is called a beam of light. 
Rays of light coming from the sun are parallel, while 
rays from a lamp or candle come to us in pencils of 
diverging rays. A medium is any space or substance 
through which light passes. 

21. Laws of Light. — The more important laws of 
the radiation of light are the following : 

l. 1. Rays of light proceed from 

every point of luminous objects in 
every direction. They proceed, for 
example, from every point of the 
sun's surface. 

2. They proceed in straight lines. 
Light, for example, comes to us in 
straight lines from the sun. 

3. They diverge as they proceed. This is illustrated 
in the figure, the central point being supposed to be 
a star, or other source of light. 

22. Divergence of Light. — By the divergence of 
rays of light is meant that they spread themselves over 




21. Give the laws of light ? 22. Explain the divergence of rays of light? 



LIGHT. 



15 




more space the further they proceed from their source. 
This is illustrated in the figure, 
where the light of a candle is rep- 
resented as passing through a win- 
dow, and illuminating a larger 
space on the opposite wall. 

23. Law of Divergence. — When the distance is 
doubled, the surface that light will cover is quadrupled. 
This is also illustrated in the figure. The wall being 
twice as far from the candle as the window, the light 
covers four times the surface. If the distance of the 
wall were three times that of the window, the surface 
covered would be nine times as large as the window ; 
if four times, the surface covered would be sixteen 
times as large. It is evident from these figures that 
the surfaces covered increase as the squares of the dis- 
tances. The light, of course, diminishes in intensity in 
the same proportion, as it is thus 
spread over greater surface. At 
four times the distance, it has 
only one-sixteenth the intensity, 
and so on. 

If a square board is placed at 
a distance of one foot, and a 
screen at the distance of two 

feet from a candle, the shadows on the screen will 
cover a space four times as large as the board which in- 
tercepts the light. If the screen is at the distance of 




23. Give the law of divergence, and illustrations ? 



16 PRINCIPLES OF CHEMISTRY. 

three feet, the shadow will be nine times as large — 
that is, three times as broad and three times as high, 
and multiplying the breadth by the height, we see that 
the space covered by the shadow increases as the 
square of the distance as shown in the figure. 

24. Reflection of Light. — If a ball of ivory or other 
material is thrown perpendicularly against any hard 
plane surface, it will return in the same line ; if it is 

thrown obliquely, it will glance off with the 
same degree of obliquity in the other direction. 
Light is reflected from plane surfaces in the 
same manner. 

This reflection is illustrated in the figure, 
which represents a mirror, and a ray of light 
falling upon it and again reflected. 

25. Apparent Place changed by Reflection. — As 
we always seem to see an object in the direction from 
which its rays enter the eye, a mirror which changes 
the direction of the rays will change the apparent place 
of the object. This is shown in Fig. 5, where the 
image of the candle is seen by reflection as far behind 
the mirror as the real candle is in front of it. The 
image is thus seen in the direction which the rays of 
light take after reflection. 

26. Concave Mirrors. — By considering that rays are 
reflected from plane surfaces with the same degree of 
obliquity with which they fall upon them, we shall be 



24. Explain the reflection of light ? 25. Explain the change of appar* 
ent place by reflection ? 26. Why do concave mirrors converge rays of 
light ? 



LIGHT. 



17 



able to comprehend how it is that concave mirrors have 
the property of converging rays of light, or bringing 
them together in a point. 




A number of small plane mirrors, situated obliquely 
toward each other, as represented in the 
figure, and as they might be arranged in 
a bowl or saucer, would evidently have 
this effect. As a concave mirror may 
be regarded as made up of innumera- 
ble plane mirrors, similarly arranged, it <^- 
would obviously be productive of the 
same effect. 



cb e> 



<p 



18 PRINCIPLES OF CHEMISTRY. 

27. Refraction. — Refraction is the change of direc- 
tion which a ray experiences in passing obliquely from 
a rarer into a denser medium, or the reverse. 

28. The figure represents a block of glass, and shows 
the direction which a ray of light w r ould take on enter- 
ing and emerging from it. On enter 

y ing, it makes a bend, and passes on 
7| through the glass less obliquely; that 
is, more nearly in the direction of a line 
drawn perpendicularly to the surface 
of the glass, and continued through it. 
On passing out again it would be bent aw T ay from such 
an imaginary perpendicular line, and resume its pre- 
vious course. 

29. Another Statement of the Law. — As the per- 
pendicular has only an imaginary existence, it is per- 
haps easier to fix in the mind the changes of direction 
of rays passing in and out at regular surfaces thus : A 
ray, on entering a denser medium, pursues w T ithin it a 
course further from the nearest portion of the surface 
than its original course would be if continued. And a 
ray entering a rarer medium takes a course nearer the 
nearest portion of the surface than its original course 
would be if continued. These statements are true for 
all plane or uniformly curved surfaces. 

30. Illustration. — A coin placed in a tea-cup, as 
represented in Fig. 8, so as to be barely concealed from 



27. W^hat is refraction? 28. Explain the figure? 29. Give another 
statement of the laws of refraction ? 80. Illustrate by a coin ? 



LIGHT. 



19 





the eye, will be rendered visible by filling the cup with 
■water. 

The surface of the 8 - 

water furnishes a 
point of transition 
from a denser to a 
rarer medium, and 
the direction of the 
ray is thereby chang- 
ed in accordance 
with the law above 
stated. It is thereby enabled to turn a corner, as it 
were, and come to the eye. 

A stick thrust obliquely into the water seems to be 
broken at the sur- 
face, because ev- 
ery part below the 
surface appears, in 
consequence of re- 
fraction, more ele- 
vated than it real- 
ly is. For a simi- 
lar reason, water 
never appears 
more than three 
fourths its true depth. 

31. Triangular Prism.— Bearing in mind the rules 
last giv^n, it will be readily seen that the course of a ray 

30. Why does a stick thrust obliquely into the water appear broken 
where it enters the water ? 31. What effect has a prism on a ray of light ? 




20 



PRINCIPLES OF CHEMISTRY. 



of light passing through a prism must be such as is 
represented in the figure. The ray may be supposed 
to start from below or above the prism. 
The line of its passage through the glass 
will be the same in either case. 

82. Let ra, n, <?, represent a section of 

a prism, l, a candle placed before it, and 

e, an eye placed behind the prism ; then 

the light from the prism will pass in the direction l, a, 

b, c, and the candle will appear to be at r, or in the 

direction that the light enters the eye. A glass luster 





from a chandelier forms an excellent prism for these 
experiments. This experiment may be made equally 
well with the water prism described in the next para- 
graph. 

33. For optical experiments the student may readily 
construct a water prism as represented in Fig. 12. A 
strip of window glass is to be scratched with a file and 



3. Illustrate the effect? 33. How may a prism be constructed? 




LIGHT. 21 

broken into three pieces of equal length. These are 

set up, as represented in the figure, upon another bit 

of glass previously warmed and thickly 

covered with sealing wax. When the wax 

is cooled, and the bits of glass which it 

holds will stand alone, the corners where 

they meet are also closed with sealing wax. 

The prism is then filled with water, taking 

care not to moisten the upper edges, and a glass top is 

afterward attached. 

34. A Lens is a transparent body having one or 
more spherical surfaces, acting on 

■J q 

the same principle as the prism, and 
it is used to concentrate or disperse 
rays of light and heat. Spectacle 
glasses are lenses used so to modify 
the light as to improve the vision. 
Sun-glasses, called also burning- 
glasses, are lenses used to concentrate rays of heat so as 
to produce fire. The sun's rays are brought to a focus 
or point, as shown in figure 13, and paper, or other 
dry substances, are readily set on fire by this means. 

35. Action of the Lens. — The surface of a convex 
lens may be regarded as composed of a great number 
of plane surfaces, and each plane surface considered 
will correspond to one side of a prism, as shown in 
figure 14, where plane surfaces a, b, 0, 5, correspond to 
the same points on the curved surface of the lens, which 

34. What is a lens ? State ita uses ? 35. Explain the action of the 
convex lens ? 




22 PRINCIPLES OF CHEMISTRY. 

receives and reflects the sun's rays, s, s', s", to a point F. 

All of the rays which 
fall upon the surface of 
the lens are bent, as 
shown in the case of the 
prism ; but, owing to its 
shape, they are bent in 
different degrees and di- 
rections, so that they all 
meet in a point. This 

point is intensely bright if brought on a dark object, 

and is called the focus. 

36. The shape of the lens causes the rays to bend in 
different degrees and directions, as above stated, in ac- 
cordance with a law of refraction according to which the 
more obliquely a ray falls upon any surface the more it 
is refracted or bent out of its course. And it is a conse- 
quence of the shape of the lens, and its greater steepness 
toward the edge, that of all the parallel rays which fall 
upon its surface, those which fall furthest from the center 
fall most obliquely, and enter the air again more ob- 
liquely. In proportion, therefore, as they need to be 
bent to be brought to the focus, they are thus bent by 
the action of the lens. 

37. Analysis of Light. — It has, up to this point, 
been assumed that light is simple in its nature, but it 
may be proved by experiment that every beam of white 
light such as we receive from the sun is made up of rays 
of different colors. 

36. Explain another law of refraction. 37. How is light composed ? 




LIGHT. 23 

38. This may be done by holding a prism in the sun 
and allowing the light to 15. 

pass through it and fall 
upon an opposite wall or 
screen. A beautiful parti- 
colored spot will be produced, called the solar spectrum. 
The beam of light which enters the prism is separated 
by it into rays of seven different colors. The experi- 
ment, if performed in a dark room, into w^hich light is 
admitted through a very small opening, is extremely 
beautiful. 

39. The rays, before entering the prism, passing along 
together parallel with each other, form white light; 
but on entering the glass and emerging from it, each 
of them is refracted or bent out of its course in a dif- 
ferent degree, and they are thus separated, and made 
to appear with their own colors. 

40. It has been proved by mathematical calculations, 
that if light consists of vibrations of ether of very 
great rapidity, the shortest vibrations would be most 
refracted or bent out of their course by passing ob- 
liquely through transparent substances. It has, there- 
fore, been inferred that the different colored rays of 
light are formed by vibrations of different rapidity. 
This is one among many other reasons for adopting the 
undulatory theory of light. 

41. Red, Yellow axd Blue are called Primary 



3S. How is its composition proved? 39. How does refraction decom- 
pose light ? 40. What theory of light serves to explain the phenomena 
of colors ? 41. Which are the primary colors ? 



24 



PRINCIPLES OF CHEMISTKY. 



GREENISH BLUE, 



ELL0W1SH GREEN 



vYELLOW 



Colors, because all other colors may be obtained by- 
suitable mixtures of these three. 

42. The relations of various colors to each other will 
be easily understood by the diagram figure 16. A circle 
is divided by three dark lines into arcs of 120 degrees 
each, and by other lines into smaller arcs ; the names 
of the primary colors are placed at the extremities of 
the darker lines, and the names of the intermediate 

colors opposite the 
lighter lines. 

43. Complementa- 
ry Colors. — If we 
take any two colors 
at opposite extremi- 
ties of the same dia- 
meter, in this diagram, 
they will together pro- 
duce white light. Thus 
red and green when 
mixed will produce white; and the same is true of 
yellow and violet, or of blue and orange. In the arrange- 
ment of colors the most pleasing effect is produced when 
one color is placed near another of which it is comple- 
mentary. The study of these principles will aid the 
development of correct taste.* 

44. Lenses decompose "White Light. — This separa- 

42. How are colors arrayed in the chromatic diagram ? 43. What are 
complementary colors ? 44. Do lenses decompose light ? 




violet red" 



REDISH ORANGE, 



RED 

CHROMATIC DIAGRAM. 



* A full development of these principles will be found in a small work by Chev- 
reul on Colors. 



ligbTt. 25 

tion of white light into colored rays always occurs when 
light passes through a prism ; but for the sake of sim- 
plicity, this fact was left out of consideration in para- 
graph 29, the object in that place being simply to show 
the general direction of the light as it passes through 
the prism. Such separation also occurs when light 
passes through a lens, but the different colored rays are 
so slightly separated as to cause but little inconvenience 
in spectacles and burning glasses. The consideration 
of the means of correcting such defects belongs to 
Natural Philosophy. 

45. Fkaunhofer's Dark Lines. — When a ray of 
sunlight, after entering a dark chamber by a very nar- 
row opening, is allowed to pass through a prism, as in 
paragraph 38, and then is examined by means of a 
telescope, certain dark lines are seen in different parts 
of the spectrum, varying in number and distinctness 
with the purity of the prism and the excellence of the 
telescope employed. The most conspicuous of these 
lines have been named from the first letters of the 
alphabet. The dark lines b and c are found in the red 
portion of the spectrum, d in the orange, e between 
the yellow and green, f in the blue, g in the indigo, 
and h in the violet. 

46. Spectroscope, Spectral Analysis. — In the 
spectrum produced by artificial light bright • lines 
are seen instead of the dark lines of the solar spec- 
trum. These lines vary in color and position with 

45. What are Fraunhofer's dark lines ? 46. What lines are seen in the 
spectrum of artificial light ? To what practical use have they been applied ? 

2 



26 PRINCIPLES OF CHEMISTRY. 

the kind of light employed. Thus soda imparts to 
flame the power of producing a double yellow line in 
the spectrum, potassium gives a pale red line, lithium 
an intensely red line, lime a deep orange and also a 
green line. The number, positions and appearance of 
the bright lines in the spectra produced by flames in 
which different substances are burning are so peculiar, 
and the quantity of material required to produce the 
effect is so small, that chemical analysis is readily affect- 
ed in that manner. A smaller quantity of any elemen- 
tary body can be detected by this process than by any 
other method. Three new metals, caesium, rubidium 
and thallium, have been discovered by this method of 
analysis. This method is called spectral analysis, and 
the instrument employed is called a spectroscope. § 612. 



CHAPTER III. 

HEAT. 

SECTION I. 

NATURE AND SOURCES OF HEAT. 

47. Nature of Heat. — It was remarked in the com- 
mencement of the chapter on light, that philosophers, 
although acquainted with its facts and laws, have dif- 
fered widely in opinion as to its nature. The same 

47. Has heat weight ? 



HEAT. 27 

is true of heat. It is agreed, however, that heat, like 
light, is imponderable, or without appreciable weight ; 
this being known from the fact that a heated body 
weighs no more than a cold one. 

48. If the end of a bar of iron is heated, the other 
end soon becomes hot. There is no doubt as to the 
effect, and it would seem that something must have 
passed from the lire, along through the rod to produce 
it. But we do not certainly know that any substance 
has been thus transmitted. It may be that heat is 
analogous to sound, and produced by vibrations. As 
in the case of light the opinion of philosophers has been 
divided upon the subject. 

49. Material Theory. — One view is that a very 
subtle fluid coming from the fire has actually passed 
along through the mass of metal, and from that into 
the hand, and so caused the sensation of warmth or heat. 
This supposed substance is called heat, or caloric. 

50. The Dynamical Theory. — Another view, corres- 
ponding to the second view of light, is, that heat is not 
a fluid, but,. like light, the result of vibration in the 
ether which is every where present. The vibrations 
which occasion in us the sensation of heat differ, of 
course, from those which produce light, as the move- 
ments of the air which produce heavy sounds are dif- 
ferent from those which produce sharp sounds ; and as 
the vibrations of different instruments, sounding the 
same note, are so different as to be readily distinguished. 
The intimate relation that subsists between light and 

49. State the material theory. 50. W^hat is the theory of vibration ? 



28 PRINCIPLES OF CHEMISTRY. 

heat renders it probable that they are different effects 
of the same cause. Great as is the apparent difference 
in their effects, it is assumed that both are the result of 
vibrations of spme kind acting upon different organs 
of sense. 

51. Illustration. — When a bell is struck its vibra- 
tions are communicated to the air, and so to the ear, 
producing the effect of sound. So, according to this 
view, vibrations of a peculiar kind are caused by some 
means in the sun, and all sources of heat, and being 
rapidly transmitted through the ether, produce, when 
they fall upon our bodies, the sensation of heat. The 
bar heated at one end becomes hot at the other, because 
certain vibrations, originated in the fire, are gradually 
transmitted through the ether, and the iron which it 
pervades, to the other end. 

52. The Facts are definitely know t n. — It is not to 
be assumed in view of the doubt which has existed as 
to the nature of heat, that a corresponding uncertainty 
belongs to the facts connected with the subject, or to 
the principles which have been derived from a study of 
the phenomena. The most positive knowledge of effects 
may exist in the presence of utter ignorance as to their 
cause. In physiology, for example, we know that mus- 
cle and bone and other parts of the body are produced 
from the blood, and that life or vital force are essential 
to their production. But as to the mode of operation 
of the vital force we are entirely ignorant. 



51. Give the illustration. 52. Show that the facts may be known 
where the nature of the cause is not understood. 



HEAT. 29 

But it can scarcely be said that any doubt exists 
among philosophers of the present day as to the nature 
of heat. Lord Bacon long ago suggested that " it is in its 
essence motion and nothing else. 55 Locke defined it as 
" a very brisk agitation of the insensible parts of the 
object which produces in us that sensation from whence 
we denominate the object hot." Davy subsequently 
supported the same view by conclusive experiments. 
It has since been most ably sustained and developed in 
the writings and experiments of later philosophers, 
among whom Mayer and Joule may be mentioned as 
especially prominent. The evidence in its favor has 
long been sufficient to satisfy the leading writers on 
chemical science. But this has not prevented their re- 
tention of the material theory as a medium of instruc- 
tion. The same course is pursued in the present volume, 
while in connection with each important topic a state- 
ment is made of the difference of conception which the 
dynamical theory requires. 

54. Definition of Cold. — Cold is a relative term 
signifying the comparative absence of heat. But the 
coldest bodies which we know of, as ice, for example, 
contain heat, and may be made colder by its withdrawal. 

55. Sources of Heat. — The principal sources of heat 
are the sun and fixed stars, chemical action, electricity, 
and friction. It is by no means certain that these 
should be distinguished as different sources ; for the 
heat of the sun may be due to chemical action, and 

53. Give Bacon's definition of heat. Locke's. 54. What is meant "by 
the term cold ? 55. State the principal sources of heat. 



30 PRINCIPLES OF CHEMISTRY. 

electricity is, as we know, excited both by chemical ac- 
tion, and by friction. 

56. Quantity of Heat the Sun sends to the 
Earth. — The sun sends enough heat to the earth every 
year to melt a shell of ice enveloping the earth a hun- 
dred feet thick. This may be ascertained by observing 
what thickness the average heat of the sun will melt 
per minute, and then calculating the quantity for a 
year. The method actually pursued is slightly different 
from this, but the same in principle. The sun, in fact, 
sends a larger amount of heat to the earth than is above 
stated, but forty per cent, of it is absorbed by the at- 
mosphere. The quantity above given is the remaining 
sixty per cent. 

57. Total Quantity of Heat the Sun gives out. — 
Knowing how much comes to the earth and its atmos- 
phere, it is easy to calculate how much starts from the 
sun. It is just in proportion to the extent of the whole 
visible heavens, as seen from the sun, compared to the 
space occupied by the earth, as seen from the same 
point. By making the calculation it is ascertained that 
a quantity of heat is given out from the sun in a year, 
which, if it all came to the earth, would melt a crust of 
ice nearly four thousand miles thick, or a quantity 
which would melt every minute a crust nearly thirty- 
seven feet in thickness. To effect this a heat is re- 
quired possessing seven times the highest intensity of 
the glowing surface of metal in a blast furnace. 



56. How much heat does the sun send to the earth ? 57. How much 
heat is given out by the sun and its atmosphere ? 



HEAT. 31 

58. Other Sources of Heat. — It is estimated that 
the fixed stars give us four-fifths as much heat as the 
sun, and that without this addition to the sun's heat, 
neither animal nor vegetable life could exist upon the 
earth. Illustrations of the production of heat by chem- 
ical action and electricity will be given hereafter. ~ 

59. Percussion. — If a leaden ball is allowed to fall 
from a height to the ground its temperature is raised. 
Its mechanical motion has, according to the dynamic 
theory, been transferred to the atoms of the mass and 
now exists as heat. Retardation of motion without 
contact also produces heat as when a diamagnetic body 
(255) is drawn back and forth through the region of re- 
pulsion between the poles of an electro-magnet. It is 
estimated that the simple stoppage of the earth in its 
orbit would develop sufficient heat to vaporize it. 

60. Heat from Friction. — The heat produced by 
slight rubbing is sufficient to set on fire a phosphorus 
match. Sir Humphrey Davy produced heat by friction 
between two pieces of ice. Count Eumford caused 
water to boil by boring a cannon beneath its surface. 
Other examples will occur to the student. The pro- 
duction of heat by friction is strong evidence in favor of 
the view that heat is a mode of motion. The unlimited 
quantity which may be produced by continuance of 
friction cannot possibly be stored up in the bodies sub- 
mitted to the process, as the material theory would 
seem to require. 

58. What is said of the heat of the fixed stars ? 59. Give an example 
of heat produced by percussion. 00. By friction. State the inference. 



32 PRINCIPLES OF CHEMISTRY. 

SECTION II. 

COMMUNICATION OF HEAT. 

61. Heat is communicated by conduction, convection, 
and radiation. These three modes of communication 
will be considered in the order in which they are 
named. 

Conduction. 

62. Conduction is the passage of heat through a 
body by communication from particle to particle. An 

^ iron wire, one end of 

"o u u u u u i"* which is held in a 

^ flame, soon grows 
hot at the other, by conduction of the heat of the flame. 
The progress of heat along a wire may be shown by 
fastening marbles to it with wax, as represented in the 
figure, and then heating one end by a lamp. The mar- 
bles drop off successively, as the heat in its progress 
melts one bit of wax after the other. According to the 
dynamical theory conduction consists in the communica- 
tion of vibratory motion from one atom to another. § 51. 

63. When Conduction ceases. — Conduction pro- 
ceeds toward the cooler portions of a body until all its 
particles become equally hot, just as the absorption of 
water by a sponge continues until all its pores are filled. 

62. Explain the conduction of heat. 63. When does conduction cease ? 



HEAT. 33 

This point being reached, there is no tendency to far- 
ther motion within the heated body. 

64. The Metals are the best Cojsdtjctoks. — The 
earths and wood conduct very slowly; fine fibrous 
substances, like wool, cotton, fur, and feathers, slowest 
of all. Liquids and gases, as will be hereafter seen, 
are non-condiiQtors of heat. The superior conducting 
power of metals is shown in the rapidity with which 
an iron wire, one end of which is held in the flame of 
a lamp, grows hot at the other end. A splinter of 
wood, or a pipe-stem, is heated from end to end much 
less rapidly, while scarcely any heat would be commu- 
nicated along a roll of cotton cloth, one end of which 
was inflamed. Wood conducts heat most rapidly in 
the direction of its fibers, and least rapidly across its 
fibers. 

65. Illustration. — The difference of conducting 
power in metals and earths may be illustrated by fasten- 
ing together by a wire, as represented 18 
in the figure, an iron nail and a bit of 
pipe-stem of equal length, and heat- 
ing them over a spirit lamp. The end 
of a match having been fastened with 
thread to each, it is found that the heat will travel along 
the nail and inflame the match at its end long before 
the other match is ignited. 

66. Protection from the Central Fire of the 



64. W T hat substances are the best conductors ? 65. How may the con- 
ducting power of metals, &c, be illustrated? 66. How are we protected 
from the central heat of the earth ? 




34 PRINCIPLES OF CHEMISTRY. 

Earth. — We are protected from the central heat of the 
earth by the non-conducting power of the rocks and 
soil which form its outer crust. So a crust forms after 
a time over the streams of lava which flow from volca- 
noes ; but, owing to its non-conducting power, the lava 
below remains liquid for years. 

67. Conduction from one Body to another. — This 
takes place more rapidly the more perfect the contact 
between the two. Conduction from air or a gas to a 
solid is slow, because the gas contains comparatively 
few atoms, and therefore furnishes few points of contact. 
Between a liquid and a solid it is more rapid, because 
there are more points of contact. A cannon ball would 
grow hot much more rapidly in boiling water than in air 
of the same temperature. Between solid and solid, again, 
conduction is less rapid, because the surfaces cannot 
adapt themselves to each other like liquid and solid so 
as to bring all their atoms together. This paragraph 
refers solely to the passage of heat from the atoms of 
one surface into those of the other. The further con- 
duction of heat depends on the substance into which 
it has passed. 

68. Heating Water. — Water is sooner heated in an 
iron pot, or other metallic vessel, than in one of porce- 
lain, glass, or earthenware, because the metal conducts 
the heat through from the fire more rapidly. Cooling, 
or the passage of heat outward when the vessel is re- 
moved from the fire, goes on more rapidly in the case 

67. When does conduction take place most rapidly ? 68. Why is water 
heated sooner jn an iron than in a glass vessel ? 



HEAT. 35 

of the metallic vessel for the same reason. These 
statements have reference only to vessels which are not 
polished. In the case of bright surfaces, another prin- 
ciple is involved to be considered hereafter. 

69. Clothestg. — Fibrous substances, such as wool, 
and furs, are best adapted for clothing both because 
they are poor conductors, and because they contain 
air shut in between their fibers, which is a non-con- 
ductor, as will be hereafter shown. The object of 
clothing is not to impart heat, but to prevent its escape 
from the body. It escapes more or less through all 
substances, but less rapidly through the fibrous mate- 
rials just mentioned, and therefore their superiority for 
winter clothing. " Cold feet" may be prevented by 
inserting one or two folds of brown paper in the boot 
or shoe. The paper is a bad conductor of heat, and so 
prevents its escape through the leather of the sole. If 
we lived in an atmosphere hotter than our bodies, the 
object of clothing would be to exclude heat, and the 
same non-conducting materials now used would be best 
adapted for this purpose also. Sometimes it is actually 
the object of clothing to keep out heat, as, when work- 
men enter hot furnaces in certain manufacturing pro- 
cesses. Thick clothing, of non-conducting materials, 
is obviously best in this case also. In summer, coarser 
fiber of linen, which is a better conductor than cotton 
or wool, is more used, because it conveys away the heat 
of the body more rapidly, as is desirable in the warmer 
season. 

69. Explain the subject of clothing and its relation to heat. 



% ft 

36 PRINCIPLES OF CHEMISTRY. 

70. Furs of Animals. — We see, in what has been 
stated, the reason why the Deity has clothed animals 
inhabiting cold climates with fine furs. While the 
elephant of the torrid zone has but a few straggling 
hairs, the polar bear has a thick coat of fine fur to keep 
in his vital heat, and enable him to endure the extreme 
rigor of a northern climate. So the sea-fowl has a 
thick covering of soft down to protect him from the 
cold of the ocean, while the ostrich has an open coat 
of scanty feathers. 

71. Warmth of Snow. — Snow keeps the earth warmer 
in winter than it would otherwise be, not because of 
any heat it imparts, but because, by reason of its low 
conducting power, and that of the air which it con- 
tains, it prevents the escape of the heat which is stored 
in the earth from the previous summer. But for this 
protecting influence of the snow, the cold of a single 
winter would be sufficient to kill whole races of plants. 
Thus, the cold of the winter weaves a garment to pro- 
tect the earth from its own influence. 

72. Building. — In building, the same principles apply 
as in the case of clothing. Bad conductors, when suit- 
able in other respects, are the best materials for walls, 
making a house cooler in summer and warmer in winter. 
Wood and brick, for example, are in this respect better 
than iron. They keep out the heat in summer, and, 
though they have the same effect to exclude the heat 

70. Why has the Deity varied the covering of animals ? 71. Why does 
snow tend to keep the earth warm during winter ? 72. How do the prin- 
ciples of conduction apply in the case of buildings ? 



HEAT. 



37 




of the sun's rays in winter, they more than make up 
for this by preventing the escape of the larger quantity 
of heat produced by the fires inside. The inhabitants 
of the Arctic regions build their winter huts of snow, 
and thus make practical use of its low conducting 
power. Double doors and windows have more than a 
double effect in preventing the escape of heat in winter, 
because of the non-conducting wall of air between them. 

73. Refrigerators. — These are double-walled wooden 
boxes, used to preserve articles 
of food from the heat of the sum- 
mer. The space between the 
double walls and top is filled 
with pulverized charcoal, which 
has in itself very little conduct- 
ing power, and again is non-conducting because of the 
air between the particles. 

74. Fire-proof Safes. — These are constructed on the 
same principle, the space be- 
tween the double walls being 
filled with gypsum, alum, or 
some other non-conducting 
material. They are used as 
repositories of valuable papers 
and other property, for greater 
security in case of fire. 

75. Sensation of Heat. — A metallic door-knob feels 
colder than the wood to which it is fastened, although 

73. What is the principle involved in the construction of refrigerators ? 
74. How are fire-proof safes constructed ? 75. How does conduction influ- 
ence the sensation of heat ? 




38 PRINCIPLES OF CHEMISTRY. 

it cannot actually be so. It is because the metal is the 
best conductor, and carries off the heat of the hand 
more rapidly. If a piece of metal and wood be placed 
in a hot oven until both become equally hot, as they must 
by long exposure to the same heat, the metal will feel 
hotter than the wood. It is because the metal, by its 
greater conducting power, supplies heat more rapidly 
to its own surface to be taken away by the hand. 

76. Simple Test of Conducting Power. — As a gen- 
eral rule, the colder a body feels, the better conductor 
it is. That this is usually the case is evident from the 
last paragraph. On applying this test, we find the me- 
tallic lamp-stand cooler, and therefore a better con- 
ductor than the table cover on which it stands. In 
an oven, or other place where the heat is greater than 
that of our bodies, the inference is reversed. For the 
flow of heat would be in this case into the hand, from 
this highly heated object, and the body that brought it 
fastest, or felt hottest, would be thereby proved to be 
the best conductor. 

77. Liquids Non-conductors. — Water in a test-tube 
may be boiled at the top while ice frozen into the bot- 

21 torn will remain unmelted. If a 

bar of metal with a cavity at the 
bottom for the ice were heated in 
the same way, the heat would be 
conducted downward so rapidly 
that the ice would soon disappear. 

76. Give a simple test for determining the conducting power of a 
body ? 77. How can it be proved that liquids are non-conductors ? 





HEAT. 39 

When a blacksmith immerses a red hot iron in a tank 
of water, the water becomes boiling hot around the iron, 
yet the water at a little distance from the iron remains 
quite cold. These experiments prove that water has 
but a feeble power of conducting heat* 

78. Fire on Water. — Fire may be kindled on water 
by pouring a little ether upon its surface and inflaming 
it. But the flame will be found to have 
slight effect on the temperature of the 
water. And, what little effect it has, is 
principally due to the fact that the glass 
or metal of the containing vessel carries 
the heat downward and distributes it to the liquid. 
When water is heated by a fire beneath it, it is not by 
conduction, but by another process, explained in a sub- 
sequent paragraph. The above experiment may be 
made in a tin cup very nearly filled with water. A 
tea-spoonful of ether having been poured on the water, 
the bottle is to be corked and set away, for fear of ex- 
plosion, from the kindling of the ether which it con- 
tains. The experiment, as described, is not in the least 
degree dangerous. 

Convection, 

79. It has been already shown that liquids and gases 
are non-conductors. This implies that they cannot be 
heated, like a mass of metal or other solid, by commu- 



78. Explain the experiment with ether to prove that liquids are non- 
conductors of heat. 79. Explain how liquids become heated. 



iO 



PRINCIPLES OF CHEMISTRY. 



23 



nication of lieat from particle to particle. Each parti- 
cle, on the contrary, receives its heat directly from the 
source of heat, and conveys it away, making room for 
others. Hence the term convection. In the process of 
boiling water, for example, the vessel of water being 
placed over the fire, the first effect of the fire is to heat 
the lower layer of liquid, and thereby to expand and 
make it lighter. It then rises as a cork would in water, 
and gives place to another portion, which becomes 
heated and rises in its turn. Thus a circulation is 
commenced, the warmer portions ascending and the 
cooler descending, which continues until the water 
boils. Before this happens, each particle will have 
made many circuits, accu- 
mulating heat with each 
return, but not communi- 
cating it to others. Air 
and gases become heated 
in the same way. 

80. Convection made 
visible. — The circulation 
above described may be 
rendered visible by adding 
a little of the " flowers of 
sulphur" to water, and 
then heating it in a test- 
tube over a spirit lamp. The suspended particles 
will be found to move in the direction indicated by 




80. How can the circulation produced in liquids by heat be rendered 
visible. 



HEAT. 41 

the arrows, showing that the water has the same mo- 
tion. The upward current is not, it is to be remem- 
bered, because of any tendency of heat to rise. Heat, on 
the contrary, travels in one direction as well as another. 
But it is, as before explained, because hot water is 
lighter than cold. Dust of bituminous coal answers 
the purpose in this experiment still better than " flow- 
ers of sulphur." It is necessary to have something that 
will neither sink nor swim, but remain suspended in 
the water. 

Convection of heat is impeded by any thing that 
makes the fluid viscid; hence porridge or starch re- 
quires to be stirred when boiling, to keep it from burn- 
ing to the bottom of the over-heated vessel. 

81. Heatestg Rooms. — The same principle explains 
in part how a room is heated by a stove. The air in 
immediate contact with the hot surface becomes heated 
and rises. Cooler air comes in from all sides to take 
its place, grows warm, and rises in turn. A circulation 
is thus established precisely similar to that which occurs 
in the tube, as represented in the figure. Any light 
object, as a feather, or a flock of cotton- wool, held over 
a stove or an open flame, will prove by its ascent the 
existence of the upward current. 

A considerable portion of heat is also communicated 
to the air of the room by direct radiation from the 
stove or other heated body, and by reflection and re- 
radiation from the objects which first receive it. In 

81. How does a room become heated ? 



42 PRINCIPLES OF CHEMISTRY. 

the case of an open fire-place, radiation is the principal 
source of heat. 

82. Convection in heating the Atmosphere. — Heat 
is distributed through the earth's atmosphere in the 
same manner. At the equator, where the surface is 
hottest, the air heated by contact with it rises and flows 
off toward the poles, while colder air from the polar re- 
gions flows in to take its place, to be heated and rise in 
turn, continuing the circulation. But for this arrange- 
ment, the equatorial regions, which are constantly re- 
ceiving excess of heat from the sun, would soon become 
uninhabitable from its accumulation, and the polar re- 
gions, from extreme cold. The currents or winds thus 
produced are subject to great irregularities, which are 
considered in works on Natural Philosophy. 

Radiation. 

83. When we stand before a blazing fire, or near any 
hot body, we become warm because heat emanates from 
the hot body and comes to us through the air. This is 
called radiant heat, because it proceeds in all directions 
from the hot body as rays of light pass from a luminous 
object. ; 

The general laws of radiation are the same for heat 
as for light. According to the dynamical theory radia- 
tion consists in the communication to the ether and 
transmission through it of the peculiar vibrations which 
constitute heat. 



82. How is the atmosphere heated ? 83. What is radiant heat ? What 
are the laws of the radiation of heat ? • 



HEAT. 43 

This theory supposes that the atoms of the body on 
which the ethereal pulsations fall themselves acquire a 
corresponding motion, and that the body is thus warmed. 

84. Heat is Radiated from all Bodies. — It is to be 
observed that while light proceeds only from certain 
bodies, heat proceeds from all points of all bodies with- 
out exception. If the mercury in a thermometer were 
frozen by extreme cold, and then hung in a cavity made 
for the purpose in a block of ice, radiation of heat from 
the ice would melt it, even if there were no air in the 
cavity to help melt it by conduction. 

85. Proportion of Radiation to Temperature. — The 
hotter a stove is the more heat it gives out. This is 
obvious, and we might naturally suppose that a stove 
twice as hot as another stove, compared with other ob- 
jects about it, would give out heat just twice as fast. 
It gives out heat, in fact, more than twice as fast, the 
rapidity of radiation being at high temperatures more 
than in proportion to the temperature. 

86. Polish is unfavorable to Radiation. — A coffee- 
pot of well brightened metal will keep its contents hot 
much better than a dingy, blackened one, thus reward- 
ing the housewife for her pains. The brightness is not 
the cause of this effect. It is owing to the increased 
density of the outer surface which accompanies high 
polish. For it is satisfactorily proved by experiment, 
that by adding to the density of a surface, its radiating 



84. Illustrate the fact that heat is always being radiated from bodies. 

85. What can be said of the proportion of radiation to temperature ? 

86. What of the influence of composition on radiation ? 



44 PRINCIPLES OF CHEMISTRY. 

power is reduced. Hot air flues are best made of 
smooth tinned iron which is a poor radiator, while 
rough sheet-iron makes the best stove pipes, because it 
has a great power of radiating heat to the room through 
which it passes. It is the outer surface of a body ex- 
clusively which influences radiation. Thus, a gilded 
globe of glass, radiates as poorly as solid metal, and the 
polished coffee-pot, used as a previous example, becomes 
a good radiator, and cools quickly, if covered over with 
paper or cotton cloth. 

Chemical constitution would seem to have an influ- 
ence on radiation. The elements are less effective ra- 
diators than compounds. The dynamical theory sug- 
gests that the atoms of heated compounds vibrating as 
they must in groups, would naturally communicate 
their motion more completely to the ether which is the 
medium of radiation. 

87. Color does not affect Radiation. — A black 
coat wastes no more of the heat of the body by radia- 
tion than a white one. But the former absorbs and 
imparts to the body more of the heat which comes to 
it associated with intense light, as is the case with the 
heat of the sun, and therefore its advantage as an arti- 
cle of winter clothing. 

88. Absorption of Heat. — Bodies differ greatly in 
their power of absorbing heat. The atmosphere is 
but little heated by the rays of the sun which pass 
through it, for we find the air grows colder as we 

87. What effect has color on radiation ? 88. How is it shown that dif- 
ferent bodies vary in their power of absorbing heat ? 



HEAT, 40 

ascend. Brick and stone walls and almost all solid ob- 
jects exposed to the rays of the sun become much hot- 
ter than the surrounding air in consequence of their 
greater power of absorbing heat. A tube filled with 
ether may be held in the focus of a burning glass with- 
out becoming sensibly hotter ; but the moment absorp- 
tion of the rays is caused in any way, as by introducing 
a bit of charcoal into the liquid, the ether boils and is 
quickly dissipated in vapor. Standing before a fire our 
clothes become much warmer than the intervening air. 
" A joint of meat might be roasted before a fire with 
the air around the joint as cold as ice." 

89. Absorption of Heat varies with the Color. — 
Dark clothing is warmer than that of light color, for 
the reason, that heat associated with light seems to fol- 
low the laws of the latter and undergo absorption or 
reflection with it. Now we know that dark objects 
owe their dark color to the fact that they absorb much 
light, and reflect but little to the eye. Experiment 
shows that they absorb much heat also. Dr. Franklin 
proved what has been stated, by the observation that 
when different colored cloths are spread upon snow, it 
melts most rapidly under those which are darkest. 

The radiating power of bodies as before remarked is 
not influenced by color, but the power of bodies to ab- 
sorb the heat of the sun's rays depends almost entirely 
upon their color. The heat from a lamp or candle is 
absorbed by differently colored objects with nearly equal 

89. What effect has color on the warmth of clothing ? 



16 PRINCIPLES OF CHEMISTRY. 

facility. Heat of low intensity is more readily absorbed 
by all bodies than beat from bodies intensely heated. 

90. Transmission. — The heat of the sun passes 
through all transparent bodies with but slight diminu- 
tion. But heat from less intense sources is absorbed, 
and in large part stopped by many substances which 
allow light to pass ; such are water and alum, and glass 
to a less extent. Thus, a glass plate will serve as a fire 
screen but not as a sun screen. For the same reason a 
glass lens fails to concentrate the heat of a fire. 

Dry air and simple gases allow heat from all sources 
to pass readily. But all compound gases and vapors ab- 
sorb in large measure heat of low intensity. Many sub- 
stances which stop the light, transmit heat very per- 
fectly. Such are black glass and smoked quartz crys- 
tal. Rock salt allows heat to pass so completely that 
it has been called the glass of heat* 

91. Reflection of Heat. — Polished metallic surfaces 
are the best reflectors. Coffee takes longer to boil in a 
bright coffee-pot, because the heat is reflected from the 
bright surface aaid does not enter the liquid. If it were 
desired to heat a liquid as rapidly as possible, and keep 
it hot as long as possible in the same vessel, it would 
be wise to take a dingy one for the rapid heating of the 
liquid, and then to polish it in order to fasten the heat in. 
Bright tea-kettles and coffee-pots with rough copper 

90. What is said of the transmission of heat through bodies ? 91. What 
bodies are the best reflectors of heat ? Illustrate the subject. - 



* According to Knoblauch even rock salt absorbs certain of the rays of heat more 
freely than the others. 



HEAT. 47 

bottoms admit the heat readily from below, and prevent 
the escape of heat at the top and sides. 

Glass mirrors do not reflect heat so well as those of 
uncovered metal, because of the absorbing power of the 
glass, mentioned in the last paragraph. But this ab- 
sorbing power is very slight for heat which comes from 
an intense source like the sun, so that such mirrors 
reflect the solar heat quite perfectly. 

92. Reflection and Absorption compared. — -The 
power of a body to reflect heat is in inverse proportion to 
its absorptive power. Both these properties depend only 
upon the surface. A sheet of gilded paper will reflect 
or absorb heat nearly as well as a plate of burnished 
gold. The heat of the sun's rays is reflected much 
more perfectly than the heat from a lamp or a candle. 

93. Equilibrium of Temperature. — It has been 
already stated that heat is constantly radiated from all 
bodies. Absorption of heat, is also universal. If any 
number of bodies are equally hot, they remain so, 
each according to its surface, imparting to the rest and 
receiving from all the others, taken together, the same 
quantity of heat. If one is hotter than the rest, it 
gives faster than it receives, until the equilibrium is 
reached. If, while they are thus coming to the same 
temperature, one is a good reflector, and therefore 
slow to receive the heat which comes to it, it is also 
slow to part with what it gets ; thus the difference of 
reflecting power is without influence. 

92. How are reflection and absorption related to each other ? 93. How 
is equilibrium of temperature maintained ? 



48 PRINCIPLES OF CHEMISTRY. 

94. Cooling of the Earth. — Were it not for the 
sun, the heat of the earth would waste away very rap- 
idly int6 space. It is, in fact, radiated into space now, 
as truly as if there were no sun or stars, but these make 
up for the loss. At night, when the sun is below the 
horizon, the waste by radiation takes place very rapid- 
ly, and the earth and air grow colder in consequence. 
It is not simply because of the absence of the direct heat 
of the sun, for this is removed at once when the sun 
sets, while the cooling proceeds until morning. As the 
earth, being solid, is a better radiator than the air, it 
cools more rapidly, sending out its heat through the air 
into space. Even in the absence of visible moisture a 
portion of this heat is returned by the aqueous vapor 
of the air. This vapor probably absorbs within ten feet 
of the surface one-tenth part of all the heat that is ra- 
diated from the earth. A part of the heat thus ab- 
sorbed is again radiated toward the earth. 

95. Ice m Tropical Climates. — To produce ice in 
some parts of India, where the temperature in winter is 
seldom below 40° Fahrenheit, excavations are made one 
or two feet deep, and loosely filled with straw, which is a 
bad conductor of heat, and upon the straw are placed 
shallow pans of porous earthenware filled with water to 
the depth of one or two inches. Radiation from the sur- 
face of the water during the clear nights rapidly reduces 
the temperature below the freezing point, and thin plates 
of ice form which at day-light are removed to ice-houses 

94. What is said of the cooling of the earth ? 95. How is ice produced 
in the tropics. 



HEAT. 49 

and kept for use in the hot season. That the water is 
not frozen by evaporation, is evident from the fact 
that it does not freeze in windy nights, when evapora- 
tion is greatest. 

96. The Formation of Dew. — Dew does not " fall," 
but is deposited from the air in contact with colder surfa- 
ces. Its deposition is another consequence of the cooling 
of the earth and the objects upon its surface by radiation. 
The air, however transparent, always contains moisture, 
absorbed and invisible. Cold causes the air, like every 
thing else, to contract, and presses out of it, as it were, 
the water which it contains. Now, when at night the 
earth has become cooled by radiation, the warmer air 
which comes in contact with it is cooled, and thus made 
to deposit its moisture in the form of dew. "When the 
temperature is sufficiently low, the dew takes the form 
of frost. 

97. "Why Clouds prevent Dew. — Clouds send back 
the heat radiated from the earth, by a new radiation, 
and thus prevent the cooling which is essential to the 
production of dew. £To dew is found therefore, on 
cloudy nights, when, if it came from above, like rain 
and snow, we should expect most. 

98. Artificial Prevention of Dew and Frost. — 
It is only necessary to substitute for clouds the artificial 
canopy of a muslin handkerchief, or any other covering, 
at a little distance from the earth, to prevent the depo- 



96. Explain the formation of dew. 97. Why do clouds prevent the 
formation of dew ? 98. How can the formation of dew be prevented 
artificially ? 



50 PRINCIPLES OF CHEMISTRY. 

sition of dew and frost. Gardeners practised this 
method of protecting their tender plants from frost 
long before philosophers explained it. 

99. Absence of Dew on polished Surfaces. — Dew 
does not form on polished surfaces, because they are poor 
radiators, or, in other words, do not allow their heat to 
escape and thereby produce the degree of cold which 
is required to form dew. Leaves and grass receive 
most dew, because they are the best radiators. 

100. Supposed Radiation of Cold. — If a piece of 
ice be held before a thermometer, it will cause the 
mercury to sink. It is not because cold has been radi- 
ated from the ice, but because the thermometer, in 
common with all other bodies, is constantly giving out 
heat, and when the ice is near, it does not get its due 
portion in return. The ice cuts off the heat that would 
have come to it from other objects behind it, and gives 
it but little in its place. 

101. Refraction of Heat. — Rays of heat from the 
sun and other objects, are refracted or bent out of their 

24 course, on passing from one 

f^ff^ro-.. medium to another, similarly 

^5^. . to rays of light. By ordi- 

^^^^^^^^p^ nary glass prisms most of 
the heat rays are refracted 
in a less degree. 

102. Heat Rays and Chemical Rays. — The light 



99. Why is dew not deposited on polished surfaces ? 100. Why does 
the thermometer fall when brought near ice ? 101. How are rays of heat 
refracted? 102. What is said further of heat rays and chemical rays? 



HEAT. 51 

which proceeds from the sun, is accompanied by rays 
of heat and others called chemical or actinic rays. In 
the analysis of light by a prism, the chemical rays ac- 
cumulate principally in the region of the violet color of 
the spectrum, while the most of the heat rays are thrown 
into the region of the red, and below it. By varying 
the source of heat which is employed the position of 
maximum temperature in the refracted beam is found 
to vary ; the less intense the source of heat the smaller 
is the refrangibility of the heat radiated. The naked 
flame of a lamp emits rays of heat of all degrees of 
refrangibility, its greatest intensity being found about 
the middle of the spectrum; the greatest heat from 
ignited platinum falls nearer to the red, and from cop- 
per at 750° nearer still, while the heat radiated from a 
surface at the temperature of boiling water contains 
scarcely any of the more refrangible rays. 

103. Neither the place of the heat rays nor of the 
chemical rays is visible to the eye, but a delicate ther- 
mometer proves that from the sun's rays there is most 
heat just below the red, and a piece of paper covered 
with chloride of silver, (a substance very sensitive to 
the chemical rays of light,) grows black most rapidly 
in the region of the violet. The place of the chemical 
and heat rays is thus shown, although neither can be 
seen. It is not to be understood that they are confined 
to the points indicated, but only that they are accumu- 
lated there in largest proportion. The positions in the 

103. How are the positions of the heat rays and chemical rays de- 
termined ? 



52 PRINCIPLES OF CHEMISTRY. 

spectrum where the greatest amount of heat rays and 
chemical rays accumulate, vary with the nature of the 
substance of which the prism is made. 

104. Burning Glasses. — The collection of rays of 
heat from the sun by ordinary burning glasses, depends 
on the fact that they are refracted, or bent out of their 
course on passing from one medium to another, pre- 
cisely as in the case of light. A lens made of two 
watch-glasses, filled with water, answers for heat as 
well as light, and may be used as a burning glass. As 
glass absorbs a great part of the heat from any artificial 
source, lenses and prisms made of glass are not suitable 
for conducting experiments on artificial heat, but in- 
struments made of rock salt should be used. 

105. Method of using a Burning Glass. — In using 
any lens, it is first to be placed near the object to be 
ignited, and then withdrawn till the spot of light which 
it casts is round and very small. The focus to which 
all the rays of light converge is thus found. The heat 
focus is a little beyond, but so near that the difference 
need not be taken into account. 

108. Different Heat Kays. — There are different 
kinds of heat rays, as there are of light rays ; some 
will pass through one substance best, and some through 
another. Thus a piece of smoked rock salt allows the 
blue heat ray of the spectrum to pass, while alum lets 
the lower or red heat ray pass. 

107. Analysis of heat. — The analysis of heat is 

104. Explain the action of burning-glasses. 105. How is a burning 
glass used ? 106. Arc all the rays of light alike ? 107. How is the ana- 
lysis of heat effected ? 



HEAT. 53 

effected by the same means as tliat of light. Rays of 
the sun are passed through a prism just as if light were 
to be analyzed, a dark colored glass being previously 
placed before the prism, to absorb the light and allow 
the heat only to pass. Emerging from the prism, it 
forms an invisible spectrum of rays beyond. These 
rays correspond to the different colored rays of light, 
and have different capacities of passing through differ- 
ent substances, as before stated. But strictly speaking, 
they have no color; they were called blue and red, 
simply to designate their relative position. Heat from 
very intense sources is more refracted than heat of less 
intensity, and it passes more readily through most sub- 
stances. This accounts for the fact that the heat of 
the sun is not stopped by glass. For the analysis of 
heat from other sources other material must be em- 
ployed for the prism. 

108. Effect of different Heat Eats in meltixg- 
Snow. — Snow melts comparatively slowly in the heat 
of the sun, because the crystalline texture of the snow 
and its white color are very unfavorable to absorption, 
but exactly suited to reflect light and heat very per- 
fectly. But near a fallen tree melting proceeds more 
rapidly, because the dark color and dense structure of 
the tree enable it to absorb the rays of the sun very 
perfectly, and becoming heated it radiates heat to all 
bodies around it, so that an additional amount of heat 
falls upon the snow near the tree. Besides this the 

108. What is said of the melting of snow ? 



54 PRINCIPLES OF CHEMISTRY, 

heat radiated from the tree is more readily absorbed by 
the snow than the heat of the sun's rays. 

109. Burning Glass of Ice. — A lens may be made 
of ice sufficiently powerful to concentrate the rays of 
the sun so as to ignite gunpowder. 

110. Change of Refrangibility of Heat. — When 
heat from a source of great intensity is absorbed and. 
again radiated it assumes a degree of refrangibility 
depending solely on the temperature of the radiating 
body, retaining no relation to the temperature of the 
source from which it originally came. When such heat 
is concentrated by lenses, or by mirrors, the tempera- 
ture of the focus of heat rays never exceeds the tem- 
perature of the surface from which the heat was last 
radiated. 

In some cases heat of low refrangibility may be 
changed to heat of great refrangibility : for example, a 
jet of mixed oxygen and hydrogen gases produces a 
heat nearly as intense as any which art can command ; 
yet such heat has a low refrangibility, and will not pass 
through glass in any considerable quantity even though 
concentrated by a lens of rock salt. But if the jet of 
burning gases falls upon a cylinder of lime it produces 
a light too brilliant for the eyes to endure, and the heat 
rays acquire the property of passing through glass and 
are highly refrangible. 



109. How can gunpowder be ignited by ice ? 110. By what means may 
the refrangibility of beat be changed? 



HEAT. 55 

SECTION III. 

CHANGES EFFECTED BY HEAT. 

111. Expansion, Melting and Yapokization are the 
principal changes effected by heat, while contraction, 
freezing, and condensation of vapor are produced by 
its withdrawal. But before these changes are ex- 
plained, it will be well to consider certain remarkable 
differences in the heating effects of beat, in the case of 
different substances. 

112. The heating Effect of Heat is different foe 
different Substances. — It might naturally be supposed 
that the same quantity of heat actually imparted to dif- 
ferent substances would make them equally hot ; but 
this is not the case. If two heated cannon balls, of 
the same size and temperature, are cooled, the one in 
mercury and the other in an equal weight of water, the 
mercury will be made much hotter than the water, by 
reception of the same heat. It does not simply feel 
hotter, as it might do if it were not really so, from the 
superior conducting power of the mercury, but it is 
actually so, as may be ascertained by testing the tem- 
perature by the thermometer. 

113. Specific Heat. — If the above experiment 
were varied, by cooling in mercury a bullet of one- 



111. WTiat changes are effected by heat ? 112. Are the effects of heat 
equal in different bodies ? 113. What is specific heat ? 



56 PRINCIPLES OF CHEMISTRY. 

thirtieth the bulk of that used for the water, the two 
would be brought to the same temperature. Mercury 
requires but one-thirtieth as much heating as an equal 
weight of water, to make it equally hot. It fills up, as 
it were, with heat, more rapidly. Iron absorbs about 
one-tenth as much heat as water. The comparative 
quantity required by any substance to produce an equal 
elevation of temperature, is called its specific heat 

The specific heats of different bodies compared with 
water as a standard are given in the Appendix. 

114. Atomic Heat. — If in the above experiment ele- 
mentary bodies are taken in the proportion of their 
atomic weights the heat required is, in most instances, 
the same. Notwithstanding some apparent exceptions, 
the inference is justified that the elementary atoms pos- 
sess the same capacity for heat. See Appendix. 

115. According to the dynamical theory, the specific 
heat of a body is the comparative amount of heat re- 
quired to produce in it the same degree of that vibra- 
tion which occasions in us the sensation of heat. 

116. Relation of Heat and Density. — The specific 
heat of any substance is diminished as its density is 
increased. Less is required to indicate the same tem- 
perature. The surplus raises the temperature. This 
is one source of the heat which is produced in hammer- 
ing metals. In the case of gases, the diminution is 
nearly proportioned to the increase of density. In the 



113. What is the specific heat of mercury ? Of iron ? 114. What is 
atomic heat? 115. What explanation does the dynamic theory give? 
116. What relation exists between density and capacity for heat ? 



HEAT. 57 

case of liquids and solids it lias been less carefully in- 
vestigated. In the comparison of different substances, 
no inference as to specific beat can be made from the de- 
gree of density. A substance more dense than another 
may at the same time have a greater specific heat. 

117. The Ocean a Reservoir of Heat. — In hot 
weather the ocean absorbs the heat of the sun and air. 
If it were an ocean of mercury, it would soon grow as 
hot as the air, and therefore cease absorbing ; but as 
water is a bad conductor and its capacity for heat is so 
much greater than that of mercury this does not occur. 
Again, in cold weather it is constantly giving out the 
large quantity it has absorbed, but at the 

same time itself grows cool, though very 
slowly. It is thus a reservoir of heat and a 
regulator of climate. 

118. Tire by Compression. — The fire sy- 
ringe, represented in the figure, is an instru- 
ment designed to produce fire by the com- 
pression of air. On forcing the piston suddenly 
down, a piece of tinder attached to the lower 
end of the piston is ignited. According to 
the material theory this is a result of the con- 
densation of the air. The specific heat of the 
air being reduced by condensation the surplus ^^ 
is forced out and ignites the tinder. According to the 
dynamical theory this case is another instance of the 
conversion of force into heat. 



117. How does the ocean serve as a reservoir and regulator of heat ? 
118. Explain the principle of the fire svriuge. 

3*" 



58 PRINCIPLES OF CHEMISTRY. 

Expansion. 

119. Expansion universal. — All bodies, solid, liquid, 
and gaseous, expand by beat, and contract to their 
original dimensions on cooling. An iron wire lengthens 
by heat ; the mercury in a thermometer expands and 
rises by heating ; air partially filling a bladder expands 
and fills it by the operation of the same cause. 

120. How Heat expands Bodies. — All particles may 
be regarded as surrounded by spheres of heat. On 
imparting additional heat to any substance, the sphere 
of each atom is enlarged, and general expansion is the 
consequence. According to another mode of viewing 
the subject, heat produces repulsion between particles 
in some unknown way, and this occasions expansion. 
According to the dynamical theory the vibrations of 
the atoms of the heated body require more space to be 
occupied by each atom than when it does not vibrate, 
just as a buzzing bee, a spinning top, or the cord of a 
violin or piano appears larger when in a state of vibra- 
tion than when at rest. 

121. Expansion of Solids. — The expansion of solids 
by heat is comparatively small. Among solids, the 
metals expand the most ; but an iron wire increases 
only g^ in length on being heated from zero up to 
212°. Expansion in general bulk is about three times 
as great as in length. Thus, a cannon ball heated to 

119. What effect has heat on the size of bodies ? 120. How does heat 
operate to expand bodies? 121. Among solids which expand the most ? 




HEAT. 59 

to 212° would occupy about ff ¥ more space than when 
cooled down to zero. 

122. Illustration. 
— The expansion of 
metals may be illus- 
trated by arranging /I 
a brick, a knitting- 
needle, and a shingle, 
as in the figure. On 

heating the needle with a spirit lamp, the shingle, if 
before carefully poised, will be overturned. 

123. Wheel-tires, Rivets, etc. — Important applica- 
tion of even this small degree of expansion is made in 
the arts. The tires of carriage wheels, for example, 
are made originally too small for the frames they are to 
surround. They are then heated red hot and applied 
in a state of expansion. The contraction which after- 
ward takes place, on sudden cooling by cold water, 
binds the wooden frame-work together with the great- 
est firmness. So in making steam-boilers, the rivets 
are fastened while hot, that they may by subsequent 
contraction unite the plates more firmly. 

124. Hot- water Pipes. — In certain uses to which 
iron is applied, the consequences of expansion have to 
be carefully guarded against. A cast-iron pipe for the 
conveyance of steam or hot water, must not be so 
laid that its ends touch two opposite walls, lest by 

122. How may the expansion of metals be illustrated ? 123. What ap- 
plication of this expansion is made in the arts? 124. What disadvantages 
arise from the expansion of metals ? 



60 TKINCIPLES OF CHEMISTRY. 

its ex-pansion when heated, the walls should be over- 
turned. 

125. Clamps in Walls. — If the two ends of a piece 
of metal are so fixed that they cannot move, and con- 
traction takes place by cold, the metal must break. 
Cast-iron clamps in walls are frequently thus broken. 
If they are of wrought iron, they often crush the stone, 
and thus loosen themselves in their sockets. 

126. Lifting Walls. — Walls of buildings, in danger 
of falling, have been restored to their perpendicular 
position by taking indirect advantage of expansion. 
This is effected, by connecting the walls to be lifted 
into place, by iron rods fixed firmly in one wall and 
passing loosely through holes in the other. The whole 
length of every alternate rod is then heated by lamps 
or pans of burning charcoal, whereby the heated rods 
are caused to expand and project beyond the wall ; the 
nuts with which the rods are provided are then screwed 
up close to the wall, when the fires being removed, the 
rods contract and draw the walls together. While they 
hold the walls in this position, the other rods in the 
series are heated in the same manner and the nuts 
upon them are screwed up, when the rods cool the walls 
are drawn still nearer together. The same process is 
repeated alternately, with one-half of the rods at a time, 
until the walls are drawn toward each other to anv % 
position required. 

125. What effect has cold upon clamps in walls ? 126. How are walls 
straightened by expansion and contraction ? 



HEAT. 61 

127. Fracture of Glass Yessels. — Glass expands 
less than iron by heat, yet sufficiently, when expansion 
is unequal on opposite surfaces, to occasion its fracture. 
Thus if hot water is poured on a thick glass plate, it 
cracks. The first effect is to expand the upper surface, 
while the under one is but slightly affected. The ob- 
vious tendency of this unequal expansion, is to warp 
the plate, and curve it inward toward the under side. 
But, as the glass cannot bend, it breaks. 

128. How to cut Glass by hot Wire. — In conse- 
quence of the same unequal expansion, a crack once 
commenced in glass may be made to follow the heated 
end of a rod of iron or pipe-stem drawn over its sur- 
face. Broken vessels of glass may be thus cut into 
useful shapes. A glass- vial may be cut evenly in two, 
by encircling it with a ring of iron heated to redness, 
and afterward plunging it into cold water. The glass 
beneath the ring becomes expanded through and 
through, and the subsequent immersion in water, causes 
a sudden contraction in the exterior, and consequent 
fracture, on the principle above stated. 

129. Wood and Marble expand little. — Wood and 
marble expand but little by heat, and are therefore 
sometimes used for pendulum rods, where careful pro- 
vision must be made against change of length by change 
of weather. 

130. Liquids expand More than Solids. — A column 



127. Explain the fracture of glass vessels by heat ? 128. How can heat 
be used to cut glass ? 129. W^hy are wood and marble used for pendulum 
rods ? 130. What is the relative expansion of water and iron ? 



62 



PRINCIPLES OF CHEMISTRY. 




of water inclosed in a glass tube, will expand 2V i* 1 
length on being heated from freezing to the boiling 
point of water, while a column of iron will expand 
only jfe. 

131. Illustration. — The overflow of 
water from full vessels before boiling 
commences, so often observed in the 
kitchen, is in consequence of expansion 
by heat. To illustrate the expansion 
of liquids, a test-tube full of water may 
be heated over a spirit lamp, as indica- 
ted in the figure. The water will be 
found to heap itself into a convex sur- 
face over the mouth of the tube, and 
even to run over, long before boiling commences. 

132. Cold Water expands by Cold. — There is an 
important exception to the general law of expansion of 
liquids by heat and contraction by cold, or withdrawal 
of heat. Yery cold water (39°F.) expands by further 
cold before it freezes. Again, on conversion into ice it 
undergoes still further expansion. 

133. Illustration. — Expansion by these combined 
causes may be shown by burying a test-tube full of 
water in a mixture of snow and salt. Before the water 
is completely frozen it will rise at least a quarter of an 
inch, above the tube. 

The greater part of this expansion is owing to the 
latter of the causes above mentioned. The freezing 



131. Illustrate the expansion of liquids by heat ? 132. What effect has 
cold on water at 39°F ? 133. How may expansion by cold be illustrated? 



HEAT. 



63 




mixture employed is made of two parts snow to one 

part salt, brought into the cup alternately 

in small portions. It is well to wrap the 

cup in flannel, or other cloth, to prevent 

loss of heat. From ten to fifteen minutes 

are required for the experiment. If the 

water is perfectly frozen, the tube will be 

found cracked by its expansion. 

134. Cold Water floats on warmer Water and 
protects it. — It was shown in the last paragraph that 
very cold water (below 39°) is in an expanded condition, 
and occupies more space 
than warmer water. It 
follows that it is lighter, 
and will float on warmer 
water. At a, b, and c, 
are shown water in sue- a b c 
cessive stages of cooling. At a the warmer water is on 
the surface ; at b the water is of uniform temperature 
throughout, and at c the colder w^ater floats upon the 
surface. 

The maximum density of water saturated with salt is 
at a temperature below its freezing point ; hence the 
phenomena in question is not conspicuous in sea-water. 
When ice forms upon sea-water it contains no salt ex- 
cept as portions of water containing salt become en- 
tangled in the forming ice. 

135. Consequences of the Lightness of very cold 




134. Why does cold water float on warmer water ? 135. What conse- 
quences result from the expansion of water by cold ? 



64: PRINCIPLES OF CHEMISTRY. 

"Water. — But for the remarkable fact that more cold 
makes very cold water lighter, and not heavier, and 
thus enables it to exert the protecting influence just 
explained, the cold of a single winter would be suffi- 
cient to kill all the fishes inhabiting our lakes and 
rivers. Another consequence would be change of cli- 
mate, as a necessary result of the formation of immense 
masses of ice, which the heat of the summer would be 
insufficient to melt. The temperate regions of the 
earth would thus become uninhabitable. Such are the 
consequences which are obviated by this remarkable 
exception to a general law of expansion. The whole 
realm of nature furnishes no more remarkable evidence 
of design on the part of the Creator. 

'As the weather grows colder each winter and 
the time approaches for the formation of ice in rivers 
and lakes, the cold water is found to float on the 
warmer, and protect it from the cold air. The body of 
water being thus protected, ice never forms many feet 
thick. The case would be very different if w T ater grew 
constantly heavier by cold. The surface water would 
then constantly sink, until all was reduced to the freez- 
ing point. Cooling does, in fact, proceed in this way 
until the temperature sinks to 39° ; then the exception 
comes in play, and the surface water, as before stated, 
retains its place and exerts its protecting influence. 
"When ice is subsequently formed it has the same effect.* 



* Recent observations by Dr. Harrison of Wallingford, Conn., show that a quiet lake 
covered with ice in winter receives heat from the earth below, and that the water at 
the bottom acquires a temperature of 40° or 42°, while the temperature of 39. £ Q , 
or temperature of maximum density, may not be more than 6 or 8 feet below the sur- 



HEAT. 65 

136. Anchor Ice. — A curious formation of ice at the 
bottom of some clear and rapid streams is sometimes 
produced by the influence of radiation in clear frosty 
weather. Ice thus formed is termed anchor ice, or 
ground ice. The water cools down as usual to 40°, 
but below this point the colder water no longer forms 
a protecting layer, as in still sheets or in streams mov- 
ing gently ; the agitation produced by the passage of 
the water through its precipitous and irregular channel 
makes the temperature uniform throughout, until it 
arrives at the freezing point. Radiation at the same 
time proceeds through the water from the weeds and 
rocky fragments in the bed of the stream ; these be- 
come now the coldest points, and to them the ice at- 
taches itself in silvery, cauliflower-shaped, spongy mas- 
ses, sometimes accumulating in quantity sufficient to 
dam up the stream, and cause it to overflow. This ice 
sometimes increases in bulk and buoyancy until it floats 
and raises to the surface portions of rock and even iron 
itself; it has indeed been productive of serious incon- 
venience by lifting and transporting to a considerable 
distance the heavy masses of iron which are used to 
prevent the removal of buoys employed to indicate the 
navigable channels of rivers. 

137. Law of Expansion for Gases. — Gases expand 

136. What is anchor ice ? 137. State the law of expansion for gases. 



face. The waters attain a condition of instability and -when the ice begins to melt 
so that the wind can agitate the water the warmer water from below soon rises and 
completes the melting of the ice in an incredibly short space of time. — Amer. Jour. 
Sci. (2) XXXV., p. 49. 



66 PRINCIPLES OF CHEMISTRY. 

T ^ r th of the bulk which they possess at 32°, for every 
degree above that point, and contract in the same pro- 
portion for every degree below it. Thus, 491 cubic 
inches at 32° would so expand as to occupy an inch 
more space at 33 °, still another inch at 34°, and at the 
same rate for higher temperatures. And the same 
quantity would contract by cold, or withdrawal of heat, 
so as to occupy an inch less space at 31°, and two inches 
less at 30°, and so on for lower temperatures. The 
law is the same for steam and other vapors. 



Measurement of Temperature. 

138. The Thermometer. — The thermometer is an 
instrument in which expansion is made use of to show 
changes of temperature. A straight wire, which w T ould 
grow regularly and perceptibly longer in proportion to 
the increase of temperature, would form the most con- 
venient thermometer. But solids do not expand enough, 
or vwith sufficient regularity, for this purpose. The 
liquid metal mercury, is therefore employed instead, 
being inclosed in a glass tube and bulb. 

139. Construction of Thermometers. — In making 
thermometers the mercury being first introduced into 
the bulb is boiled so as to expel all air and moisture, 
and fill the tube with its own vapor. The end of the 
tube is then closed by fusion. As the metal cools, it 



138. What is a thermometer ? 139. How are thermometers manufac- 
tured ? 



HEAT. 67 

contracts and collects in the bulb and lower part of the 
tube, leaving a vacuum above. The instrument is 
now complete, with the exception of graduation. Used 
in this condition, the mercury would be observed to 
rise and fall with changes of temperature, but we should 
not be able to say how much or how little. 

140. Graduation of Centigrade Thermometer. — 
To obtain a fixed point from which to count, the instru- 
ment is immersed in melting ice, and the point to which 
the mercury sinks scratched on the glass. This 
point is called zero. Another fixed point is ob- 
tained by immersing the thermometer in boiling 
water, and when the mercury has risen, noting 
this height also on the glass, and marking it 100°. 
The space between the two points is next divided 
into one hundred equal parts, by scratches on 
the glass, and numbered from one up to a hun- 
dred. The upper and lower portions of the 
tube are marked off into divisions of the same 
length, for very high and low temperatures. 

A thermometer graduated as above is called 
a Centigrade thermometer, from the fact that 
the space between " boiling" and " freezing" is 
divided into one hundred degrees. This is by far the 
most rational method of graduating, and these ther- 
mometers are in general use on the continent of Europe, 
and by scientific men all over the world. 

140. How are thermometers graduated ? Describe the Centigrade ther- 
mometer. 



68 PRINCIPLES OF CHEMISTRY. 

141. Fahrenheit's Thermometer. — This is the ther- 
mometer in common use in this country. The instru- 
ment itself is precisely the same as the centigrade. 
The difference is only in the graduation. In graduat- 
ing it, the space between the freezing and boiling 
points having been marked on the glass is divided into 
one hundred and eighty parts, and the rest of the tube, 
above and below, into similar spaces. 

Fahrenheit adopted for the zero of his scale the low- 
est temperature known in his time, produced by mixing 
snow and salt. The same degree of cold had been 
previously observed in Holland in 1709. This temper- 
ature was then supposed to indicate an entire absence 
of heat, but as a much lower temperature has since 
been observed by arctic travelers, and a still greater 
degree of cold can now be produced by artificial means 
there ceases to be any propriety in placing the zero 
point where it was established by Fahrenheit. The 
reasons which induced Fahrenheit to make 180 divisions 
between the freezing and boiling points have no scien- 
tific importance, and therefore the Centigrade gradua- 
tion is much to be preferred ; but as the scale of Fah- 
renheit is much better known in this country it is 
generally used in elementary books. 

If a thermometer of each kind were immersed in 
boiling water, the mercury would rise in the Centi- 
grade to the point marked 100, and in the Fahrenheit 
to the point marked 212. In the same way, zero Cen- 

141. Describe Fahrenheit's thermometer. 



HEAT. 



69 



31 



tigrade corresponds to 32° Falireiilieit. The two ther- 
mometers are compared in figure 31. 

142. Extreme Cold, how measured. — 
As the temperature is lowered, the mer- 
cury of the Fahrenheit thermometer sinks, 
until by sufficient cold it reaches 39 de- 
grees below zero. More intense cold has 
no further effect, for at this point the 
mercury freezes. How much colder it is 
than — 39° cannot be told, therefore, by 
the mercurial thermometer. Thermome- 
ters containing alcohol instead of mercury 
are used for this purpose, because alcohol 
never freezes and will continue to sink 
farther and further in the tube the colder 
it grows. " ^=^ 

143. Absolute Zero. — It has been stated that gases 
expand ¥ | T part of their volume for every degree of 
heat above 32° F. and contract a like amount for every 
degree below 32°. If the same rate of contraction 
continued for every degree of cold, at 491° below freez- 
ing, or at 459 below the zero of Fahrenheit, the vol- 
ume of a gas would disappear and there could be no 
further contraction, some philosopher^ therefore think 
there must be an absolute zero. On the vibratory 
theory of heat there also should be an absolute zero 
where the molecules of all bodies are in a state of entire 



142. How is extreme cold measured ? 143. What reasons are given for 
supposing there is an absolute zero ? 



70 PRINCIPLES OF CHEMISTEY. 

rest, but where that zero is can at present be only a 
matter of conjecture. 

144. Extreme Heat, how measured. — If a Fahren- 
heit thermometer is heated, the mercury in it rises until 
it readies 662°, and then begins to boil. A little more 
heat forms sufficient vapor of mercury to burst the 
tube. For this reason, a mercurial thermometer can- 
not be used to measure extreme heat. A platinum bar 

32 inclosed in a black lead tube shut at the bot- 
tom, is commonly employed for this purpose. 
Tube and bar are placed on the fire, or in the 
melted metal whose heat it is desired to meas- 
ure, one end being left out, so that it can be 
seen. The consequence is that the platinum 
bar expands, and projects from the earthen 
tube. The tube itself expands but little. The further 
the bar projects, the greater is the heat. As it pushes 
out, it is made to move an index hand, and point to the 
number indicating the temperature, on a graduated arc. 
This arc is first graduated by repeated trials, observing 
how much the bar projects and moves the hand by the 
same heat which raises the mercury one degree in the 
Fahrenheit thermometer. 

145. The Air Thermometer. — A column of air con- 
fined in a glass tube over colored water, was the first 
thermometer used. Heat expands the air and length- 
ens the column downward, pushing the water before it, 



144. How is extreme heat measured ? 145. Describe the air thermom- 
eter. 



HEAT. 71 

while cold has the contrary effect. The temperature is 
thus indicated by the height at which the water stands. 

146. Theemo-Electeic Pile. — For the detection of 
slight variations of temperature an instrument called 
the thermo-electric pile is employed. In its simplest 
form it consists of a bar of bismuth and a bar of anti- 
mony soldered together at one end. The two bars are 
connected at the other end by a metallic wire which 
contains a galvanometer in its circuit. The slightest 
warming of the soldered junction generates a current 
of electricity. This current circulates through the gal- 
vanometer and produces a deflection of the needle. (305) 

Liquefaction. 

147. Solids become Liquids by Heat. — On being 
heated up to a certain point, solids are melted, or con- 
verted into liquids. Thus, at all temperatures below 
32°, water is solid ice, but the moment it is warmed up 
to this point, by change of weather or other means, it 
begins to melt. The temperature at which this change 
occurs is called the melting point. 32° is therefore the 
melting point of ice. The melting point of sulphur is 
226° ; that of lead, 612°. 

148. All Substances are fusible. — All substances 
are fusible, or in other words, may be melted ; but the 
melting point of all is not definitely known. Thus, 
carbon has been fused by the heat of the galvanic bat- 
tery, but it is impossible to state the melting point in 

146. What is the thermo-electric pile ? 147. How do solids become 
liquids ? 1-18. Are all substances fusible ? 



72 PRINCIPLES OF CHEMISTRY. 

degrees. Under great pressure, increased heat is re- 
quired to effect fusion. Thus the melting point of 
sulphur is raised from 226° to 285°, by a pressure of 
11,880 lbs. to the square inch. There are exceptions 
to this law. 

149. Disappearance of Heat in melting. — Melting 
or fusing is effected by heat, and a remarkable circum- 
stance attending it, is the disappearance of the heat 
which has effected the change. Thus, if a thermome- 
ter be applied to ice or snow which has just begun to 
melt, it will be found to stand at 32°. Let the ice be 
then introduced into a tumbler, and placed on a stove, 
and the temperature again tested at the moment when 

the conversion into water is completed : 
The thermometer will be found again 
to stand at 32°. The water produced 
is no hotter than the original ice, yet 
heat has been pouring into it, through 
the bottom of the vessel, during the 
whole process of melting. If a piece 
of glass of the same size had been sub- 
jected to the same heat, it would have 
grown constantly hotter. It follows 
that in the case of the ice there has been a disappear- 
ance of heat. This disappearance always occurs when- 
ever a solid is converted into a liquid. 

150. Explanation. — According to the material the- 
ory the disappearing heat exists in the liquid as com- 

149. What remarkable circumstance attends the melting of bodies? 
150. How is this explained by the dynamical theory ? 




HEAT. 73 

hined or latent heat, just as an acid exists latent in 
every salt. According to the dynamical theory the 
heat which disappears in melting (as also in boiling) is 
consumed in overcoming cohesion. It has been con- 
verted into potential force which now resides in the 
separated atoms just as potential energy resides in a 
lifted weight ; when the lifting ceases, the weight falls 
and the force is developed. So when the heating ceases 
" the atoms clash together with a dynamic energy equal 
to that which separated them, and the precise quantity 
of heat then consumed now reappears." 

151. Freezing Mixtures. — "When solids take a liquid 
form by other means, as, for example, when salt dis- 
solves in water, the temperature is generally much re- 
duced. Nitre, for example, reduces the temperature 
of water in which it is dissolved from 15 to 18 degrees, 
and is therefore much used in the East, where it is 
abundant, for cooling wines. Mixed nitre and sal- 
ammoniac have a still greater effect. Sulphate of soda 
drenched with strong muriatic acid, will reduce the 
temperature from 50° F. to zero. 

152. When two solids, on being mixed, become both 
liquid, still greater cold is often produced. This is the 
case with a mixture of snow with common salt, or with 
chloride of calcium. By the former mixture, used as 
shown in paragraph 133, ice-cream is frozen.* By the 

151. Mention some freezing mixture. How do they produce cold? 
152. Mention other freezing mixtures, Why do they produce greater 
cold? 



• Fahrenheit regarded the temperature thus produced as absolute cold, and there- 
fore assumed it as the zero of his scale. 

4 



74 PRINCIPLES OF CHEMISTRY. 

latter mixture, a cold sufficient to freeze mercury may 
readily be produced. For this purpose, three parts of 
the chloride of calcium are to be mixed with two of 
dry snow. 

153. The Melting of Snow cools the Air. — When- 
ever ice is converted into water, whether rapidly by fire 
or slowly by change of weather, the disappearance of 
heat, above mentioned, occurs. Thus, when the snow 
melts in spring, heat is drawn off from the air and 
made latent, or combined in the water which results 
from the melting. This makes the weather cooler than 
it would otherwise be, and retards in a measure the ad- 
vance of spring. 

154. Freezing. — Liquids become solids by the re- 
moval of their combined heat. Thus, if molten lead 
is allowed to stand awhile, the heat which it contains 
passes away into other objects, warming them ; and the 
metal itself, having lost its heat, becomes solid. So in 
winter, the combined heat which is contained in water, 
is conveyed away by the colder air, and the water, hav- 
ing lost its heat, is converted into ice. 

155. Freezing Point. — The temperature at w T hich a 
substance passes from the liquid into the solid state is 
called the freezing point. Thus 32° is the freezing 
point of water. The freezing point of any substance 
is, as might be supposed, the same as the melting point. 
Water, for example, becomes ice in process of cooling, 



153. How does the melting of snow affect the weather ? 154. How do 
liquids become solids ? 155. What is the freezing point of a liquid ? 



HEAT. TO 

at the same temperature that ice becomes water in pro- 
cess of heating. 

158. All Liquids have theik Freezing Point. — 
There is good reason to believe that ail liquids, without 
exception, have their freezing point, but the reduction 
of temperature requisite has not in the case of all been 
attained. Alcohol and ether, for example, have never 
been frozen. 

157. In Freezing, Latent Heat becomes Sensible 
Heat. — If water, in sufficient quantity, is taken into 
an apartment where the temperature is several degrees 
below the freezing point, and then allowed to become ice, 
it will be found that the freezing process has actually 
warmed the apartment several degrees. The latent 
heat has been drawn off by the colder air of the room, 
raising its own temperature, and leaving the water in 
the condition of ice. 

158. Cellars warmed by Ice. — In accordance with 
the principles above stated, tubs of water are some- 
times set to freeze in cellars, thereby to prevent exces- 
sive cold. And even in the coldest climates a sufficient 
supply of water might thus bemade to secure an apart- 
ment against extreme cold. 

159. Effect on Climate. — The milder climate of 
the vicinity of lakes which are accustomed to freeze in 
winter, and the moderation of the weather during a 
snow storm, are accounted for on the same principle. 

156. Can all liquids be frozen ? Give examples. 157. In freezing, 
what becomes of the latent heat ? 158. How can cellars be warmed by 
ice? 159. W r hat effect has the freezing of water on climate ? 



76 PRINCIPLES OF CHEMISTRY. 

As the melting of snow retards in a certain degree the 
advance of spring by the heat it abstracts from the at- 
mosphere, so the formation of ice tends to make the 
advance of winter less rapid, by the heat which it 
evolves. 



Vaporization. 

160. Formation* of Vapors. — Unlike melting or 
liquefaction, vaporization occurs gradually, and through 
a wide range of temperature. Thus water at all tem- 
peratures, and even ice, yield vapor. But there is a 
limit for each substance below which its evaporation 
does not occur. 

181. Vapors Transparent. — All vapors are perfectly 
transparent, like the atmosphere. If water be boiled 
in a flask, it will be found that the steam within the 
flask is as transparent as air. The steam thrown from 
a locomotive would be invisible if it remained steam. 
We should hear its roar, but see nothing. 

162. Density of Vapors. — Vapors are of all degrees 
of density. The vapor of water may be as thin as air, 
or, again, almost as dense as water itself. 

163. Elasticity of Vapors. — All vapors are elastic, 
like air. Steam, like air, if compressed in a cylinder, 
with a close fitting piston, by a heavy weight, would 
expand again, and force the piston out, as soon as the 

160. What is said of the formation of vapors ? 161. What is the ap- 
pearance of vapors ? 162. Is the density of vapors uniform ? 163. Illusi 
trate the elasticity of vapors. 



HEAT. 77 

weight were removed. The force with which a vapor 
expands, or strives to expand, supposing the weight not 
removed, is called its elastic force or tension. 

184. Density depends on Temperature. — The va- 
por produced at ordinary temperatures by evaporation 
from the sea and the moist earth, is less dense, or in 
other words, contains less water in the same volume, 
than that formed during the heat of summer. Ordi- 
nary steam, or aqueous vapor, produced at 212°, has 
still greater density. Steam produced at 250° has 
double the density of ordinary steam, and by increas- 
ing the temperature to 294°, the density is again 
doubled. Steam of higher temperature than 212° can 
only be produced in closed vessels, or those with an 
imperfect vent. The law is the same in case of other 
vapors — the higher the temperature the greater the 
density, provided a surplus of the material from which 
the vapor is produced is present. But if this is not 
the case, heat has simply the effect of expanding the 
vapor as it would an equal quantity of air. In the 
case of a partial supply of water, the vapor grows 
more dense, but does not reach the highest density 
which it would have at the same temperature with a 
full supply. 

165. Disappearance of Heat in Yapoks. — The 
same disappearance of heat which occurs when a solid 
is converted into a liquid, occurs also when a liquid is 
converted into a vapor or gas. Thus, if we wish to 

164. How does temperature effect density ? 165. Wliat remarkable cir- 
cumstance attends the formation of vapors ? 



78 PRINCIPLES OF CHEMISTRY. 

cool a room in summer, we sprinkle the floor. As the 
water evaporates, much of the heat of the room disap- 
pears. It has entered into combination with water to 
produce vapor, and has no longer the power of affecting 
the senses and the thermometer. In the same manner, 
our bodies are cooled in summer by the constant evap- 
oration of moisture from the surface. All vapors may, 
indeed, be regarded as combinations of heat with the 
liquids from which they are formed. In this case, also, 
the heat which becomes latent in thus combining, is 
called latent heat. (150). 

166. Freezing by Evaporation. — The more rapidly 
a substance evaporates, the more heat does it require 
for the evaporation. This it obtains from objects in 
contact with it. Ether may be made to evaporate so 
rapidly as to freeze water, even in summer. This is 

34 best accomplished by covering the bottom of a 
test tube with a cotton rag, or several layers of 
porous paper, as represented in the figure, dip- 
ping it into ether, and then waving it to and fro 
in the air, or spinning it between the palms of 
|j| I the hands. By repeating this process several 
times, a few drops of water, previously placed 
in the tube, may be frozen. A mixture of liquefied 
carbonic acid and nitrous oxide gases, previously lique- 
fied, produce on evaporation a temperature of 220 de- 
grees below zero. 

167. The Cryophorus or Frost-bearer. — This in- 

166. How can ether be made to freeze water ? Explain its action. 
167. Describe the cryophorus. 



. HEAT. 79 

strument which was invented by Dr. Wollaston, con- 
sists of a tube with a bulb on one extremity, and an 
enlargement or bulb at the other end containing water. 
The air is expelled from the instrument by boiling the 
water in both bulbs at the same time and allowing the 
steam to escape at the 35 



opening at <?, which is { — 
then hermetically seal- () 
ed in a blow-pipe flame. 



"When the empty bulb is placed in a mixture of snow, 
or pounded ice, and common salt the condensation 
of the vapor with which the whole instrument is filled 
causes such rapid evaporation that the remaining water 
is frozen. 

188. Protection from Heat by Evaporation. — By 
previously moistening the fingers, they may be dipped 
unharmed, for an instant, into molten lead, or passed 
through a stream of white-hot iron as it flows from the 
furnace. A cloak of comparatively cool vapor is formed 
from the moisture upon the fingers, and keeps them 
from contact with the molten metal. 

169. Relations of Air and Vapor.— The earth is 
surrounded by air to the height of fifty miles. It is 
also surrounded by vapor occupying the same space 
which the air occupies. But they are independent of 
each other. Each contracts for itself, and expands for 
itself, according to the temperature. When more vapor 
i3 produced by evaporation from the sea, or other 

168. How does evaporation protect from heat ? 169. Does vapor dis- 
place air ? 



80 PRINCIPLES OF CHEMISTRY. 

sources, it rises into the air without displacing it or 
pushing it aside, only rendering the vapor which it be- 
fore contained more dense, mingling with it and occu- 
pying a portion of space which was previously entirely 
filled by the air alone. 

170. Quantity of Yapor in the Atmosphere. — 
The air is always full of vapor; that is, where there is 
a cubic inch of air, there is a cubic inch of vapor with 
it, occupying the same space. 

171. Quantity of Water the Air may contain as 
Yapor. — As the density of vapor is dependent on tem- 
perature and the supply of material to be vaporized, it 
is obvious that the quantity of water present in the air 
in the form of vapor, varies according to temperature 
and locality. In summer, and over the sea, it is com- 
monly greatest. At a medium summer temperature of 
75 degrees, the vapor in the air is sometimes so dense 
that every cubic yard of air contains a cubic inch of 
water, in this form. But it can never, at this tempera- 
ture, contain more. It is then said to be " saturated," 
and also that its capacity for water is filled. 

172. Capacity of the Air for Water increased 
by Heat. — As the weather grows warmer, the capacity 
of the air for moisture is increased, so that at 100° it 
can contain twice as much as at 75°, or two cubic 
inches. On the other hand, as the weather grows 
cooler, its capacity is diminished, so that at 50° it can 



170. What quantity of vapor exists in the air ? 171. Upon what does 
the quantity of water in the air depend ? 172. What effect has heat upon 
the quantity of vapor present in the air? 



HEAT. 81 

hold scarcely more than half a cubic inch, and is satu- 
rated by this comparatively small quantity. In general, 
the capacity of the air for moisture is increased by the 
elevation of its temperature. 

173. Effect of Wind. — "Wind causes evaporation to 
proceed more rapidly, not because the air in motion has 
any greater capacity for moisture, but because new 
portions of air are brought successively into contact with 
the wet surface. As fast as one portion has imbibed a 
certain amount of moisture, another portion of drier 
and more thirsty air takes its place. 

174. Deposition of Moisture. — It follows that air 
that is saturated, or, in other words, has its full portion 
of moisture in the form of vapor, must deposit a por- 
tion of it in the form of water in cooling. Thus a 
cubic yard of saturated air at 75°, on being cooled 
down to 50°, would yield half a cubic inch of water, or 
half of the whole quantity which it originally contained. 
If we suppose the experiment to be performed in a 
glass vessel where the effect of cooling could be ob- 
served, we should first see a mist or dew within the 
box, consisting of the particles of water which the 
colder air can no longer retain. This mist would gra- 
dually deposit and collect in the form of water, and if 
measured, would be found to make more than half a 
cubic inch. Something less than half a cubic inch 
would remain as invisible vapor in the cooled air. If 



173. How does wind effect the quantity of vapor in the air ? 174. Ex- 
plain the deposition of moisture. 



82 PRINCIPLES OF CHEMISTRY. 

the air were cooled further, part of this would be con- 
densed to water. 

175. Unsaturated Air. — Air that does not contain 
its complement of water will not yield any by slight 
cooling. It would be like slightly compressing a half- 
filled sponge. But as the cooling proceeds, the vapor 
becomes so dense that further cooling will cause a 
deposition of moisture. A cubic yard of air at 75°, 
containing only half a cubic inch of water in the form 
of vapor, would yield none on being cooled down to 
50°. At this point the formation would commence. 
If it contained originally less than half a cubic inch, it 
would have to be cooled still lower before any moisture 
made its appearance. The less the moisture, the more 
cold it would require to wring it out. 

176. Quantity of Yapor in the Atmosphere. — As 
has been already stated, the capacity of air for vapor 
is in proportion to its warmth. The air of summer 
therefore generally contains more moisture than that 
of winter. But this is not necessarily the case, for 
the capacity for moisture is not always filled. Hot air 
over a desert, for example, contains less moisture than 
cold air over the sea. And in the same locality, and 
during the same season," the quantity of moisture in the 
air will differ from day to day, and from hour to hour. 
This will depend a good deal on the wind, whether it 
blows from the land or from the sea. Sometimes it 



175. What is said of unsaturated air and its moisture ? 176. Is the 
quantity of vapor in the atmosphere always proportionate to its warmth ? 



HEAT. 83 

contains a cubic inch of water in the form of vapor in 
every square yard, but generally less. 

177. Mist and Fog. — These are aqueous vapors, ren- 
dered visible by the cooling of the air, as before ex- 
plained. "When the moisture of the air is deprived of 
the latent heat which converted it into invisible vapor 
it becomes visible as mist or fog, which consist of ex- 
ceedingly minute vesicles or hollow globes of water 
containing air, which float about in the atmosphere 
just as soap-bubbles blown up by boys at play. Steam 
which issues from a boiler or the spout of a tea-kettle 
is at first invisible, but as it meets the air a portion is 
suddenly cooled and becomes visible as vesicular water 
or fog, but as soon as it mingles with a sufficient 
amount of air it again becomes an elastic vapor and 
entirely disappears. When the air is saturated, the 
least cooling will produce a fog, as in the case supposed 
in paragraph 174. "When it is not saturated, more cool- 
ing will be required, as in the case supposed in the sub- 
sequent paragraph. The beautiful veil of mist, which 
forms in summer-nights over low places, is owing to the 
cooling of the air below its point of saturation, which 
takes place after sunset. 

178. Mixed Currents of Aik. — The phenomena of 
mist, fog, clouds, and consequently of rain, are more 
commonly owing to the mixture of cold and warm 
winds or currents of air. When this admixture takes 
place, the warm air becomes colder, and tends to de- 

177. What is the cause of mists and fogs ? 178. Explain the produc- 
tion of fogs by mixed currents of air. 



84 PRINCIPLES OF CHEMISTRY. 

posit its moisture, and the cold air warmer ; and it 
miglit be at iirst supposed that those two influences 
w r ould counteract each other. For example, if a cubic 
yard of air at 100° mixes with a cubic yard at 50°, they 
both become 75°, and it might be thought, that the 
warming of the colder cubic yard would increase its 
capacity for moisture, as much as the cooling of the 
warmer cubic yard would diminish its capacity, and 
that consequently no mist would be produced. But, 
as before stated, it has been ascertained by experiment 
that hot air at 100° will contain about two cubic inches, 
and air at 50°, about half a cubic inch of water. The 
two would therefore contain about two and a hall' cubic 
inches. But air at 75° can hold only one cubic inch, 
and consequently the two cubic yards would hold but 
two cubic inches. The surplus half inch would con- 
sequently take the form of visible moisture, called 
cloud, fog, or mist, according to circumstances. It is 
not to be understood, from what is above stated, that 
half a cubic inch of water is always yielded by every 
two cubic yards of air at 50° and 100° which come to- 
gether ; if they are not totally saturated, the quantity 
will be less. 

179. Fogs on the Sea-Coast. — The sea is cooler 
than the land in summer, and warmer in winter. As 
a consequence, the air above the sea is cooler in sum- 
mer and warmer in winter, than that above the land. 
The admixture of these bodies of air, which takes 

179. Why are fogs produced on the sea-coast ? 



HEAT. 85 

place along the coast, produces fogs on the principle 
above stated. 

180. Fogs on Rivers. — When land and water have 
the same temperature, as may be the case with small 
lakes and rivers, the difference of radiation during a 
single night often produces fogs. The land cools more 
rapidly than the water. As a consequence, the air 
above the land is cooler than that above the water. As 
the two bodies of air mingle, fog is produced, and is 
seen following the devious course of the river, or brood- 
ing over the lake in the morning. 

181. Newfoundland Fogs. — The fogs on the banks 
of Newfoundland are owing to the mixture of cold 
winds from the north, with the warm air of the Gulf 
Stream, which passes along that part of the ocean. 

182. Cloud-capped Mountains. — The temperature 
of the air at high elevations is always lower than at 
the general level of the earth. As the warm breeze 
comes up from the warmer valleys, the two currents 
mingling produce clouds. A clear atmosphere through- 
out a whole day is rare, on high mountains. 

183. Dew Point. — It has been already seen that air 
has to be cooled more or less before it yields moisture, 
according to the amount which it contains. If it con- 
tains about one cubic inch to the cubic yard, or, in 
other words, is saturated, the least cooling will cause 
the appearance of visible moisture. If it contains half 



180. Why do fogs form on rivers ? 181. What causes the Newfoundland 
fogs ? 182. Why are clouds produced on high mountains ? 183. What is 
the dew point ? 



86 



PRINCIPLES OF CHEMISTRY. 




as much, it must be cooled down to 50° F. If it con- 
tains less than half as much, still more refrigeration is 
required. The temperature at which the deposition 
begins in any case is called the dew point. 36 

184. HOW TO FIND THE DeW POINT. 

— It is commonly found by^adding ice, 
little by little, to a glass of water con- 
taining a thermometer. As the water 
grows cool, the glass cools also, and as a 
consequence, the exterior air immedi- 
ately in contact with it. After a time, 
moisture begins to deposit. The tem- 
perature at which this occurs is noted, 
and is the dew point. 

185. Dew. — The earth cools, as has before been stated, 
every clear night, by radiation. The air in immediate 
contact with it, becomes thereby so much cooler, that 
it cannot retain all its water in the form of invisible 
vapor, and the deposition of the surplus in the form of 
dew is the consequence. 

186. Grass and foliage receive most dew because they 
are good radiators, and exposing to the air a great ex- 
tent of surface they lose their own heat rapidly and 
cool down the air sufficiently to cause a deposition of 
its moisture. The soil and stones receive less dew or 
none at all ; because though they are good radiators, 
they have but a very small extent of surface in propor- 
tion to the stores of heat they contain : they are also 



184. How can the dew point be found ? 185. Explain the formation 
of dew. 186. Why do grass and foliage receive the most dew ? 



HEAT. 87 

constantly receiving heat from the ground below, so 
rapidly that they do not become sufficiently cool to 
produce a rapid deposition of dew. Dew does not form 
on a cloudy night, because the clouds radiate heat to 
.the earth and thus prevent the requisite cooling. 

187. Capacity for Yapor : Expansion not the 
Cause. — It must not be supposed that the increased 
capacity of the air for vapor, which results from heat- 
ing, is owing to its expansion. Air does indeed ex- 
pand about one-twentieth between 50° and 100°, but 
its capacity for moisture is quadrupled by the same rise 
of temperature. 

188. Absorption not the Cause. — It is not uncom- 
monly supposed that the air acts to absorb vapor as a 
sponge does to draw up water. The term " saturated" ■ 
used for convenience in scientific works, is calculated to 
give this impression. But vapors are found to rise, 
even more rapidly, into a vacuum, or space from which 
all the air has been removed. 

189. Increased Density of Yapor the Cause. — 
The air receives any vapor that may be formed, whether 
more or less dense. At higher temperatures, denser 
vapor is produced. It follows that the air will contain 
more water, in proportion to the elevation of its tem- 
perature. 

190. Removal of Air does not increase the 
Quantity. — It might be supposed that more water 

187. How is it known that the increased capacity of air for moisture 
is not clue to expansion ? 188. WTiat proves that absorption is not the 
cause ? 189. What then is the cause ? 190. Does the removal of air in- 
fluence the formation of vapor ? 



88 PRINCIPLES OF CHEMISTRY. 

would rise into a vacuum in the form of vapor than 
into a space filled with air, on the ground that the re- 
moval of the air would make more room for something 
else. It is found, however, that the presence or absence 
of air makes no difference in the quantity,* though it 
takes a longer time to fill a given space with moisture 
when it is filled with air. 

191. Several Vapors may occupy the same Space. 
— It follows from the last paragraph that vapors do not 
displace the air ; they penetrate it instead. It is a re- 
markable fact, that a number of vapors may occupy the 
same space without interfering with one another ; and 
each in the same quantity as if the rest were absent. 

192. As much water will rise in vapor into a jar of 
•air as if it were a vacuum. And in addition to this, 
as much alcohol and ether successively, as if the jar 
were entirely empty. 

193. If the elastic force or tension of air is increased, 
it expands. Vapors possess elastic force as well as air. 
A mixture of air and vapor has the combined tension 
of both. The tension of aqueous vapor at 80°, being 
3V that of the air, it produces, on rising into the air, 
an expansion of ¥ l £+. As the weight of the air is not 

191. Do vapors and gases exclude each other? 192. Give examples. 
193. Why is moist air lighter than dry air ? 



* This statement relates to vapors rising into a confined space. In unconfined 
space, expansion of the mixture occurs, which is equivalent to displacement in the 
same proportion. (§ 193.) 

t Steam at 212° having tension equal to that of the air, would double the volume. 
Gases and vapors, with the density they possess when collected in the usual manner, 
by displacement of mercury or water, would have the same effect, and thus, like 
steam, displace their own volumo of air. 



HEAT. 89 

increased in the same ratio, ordinary moist air is lighter 
than dry. 



Atmosphere . — Boiling. 

194. "Weight of the Atmosphere. — As an introduc- 
tion to the subject of boiling, it will be necessary to 
consider the pressure of the atmosphere. The earth is 
surrounded by an atmosphere, estimated to be fifty 
miles high. It is very light compared with the earth 
itself, or with water. But it has weight, as may be 
proved by weighing a bottle full of air, and then pump- 
ing out the air and weighing it again. The empty bot- 
tle will be found to weigh less than the bottle full of 
air. 

195. Another Proof of the "Weight of the Air. — 
That the air has weight, is again proved by tying a 
piece of bladder over one end of a glass cylinder, 
placing the other end air-tight on the plate of an 
air pump, and then exhausting the air. The pressure 
of the column of air that stands on the bladder is 
sufficient to break it, and the air settles in, as ef- 
fectually as if it were a column of iron. The atmos- 
phere exerts such pressure, amounting to about fifteen 
pounds to every square inch, on all parts of the earth's 
surface. 

198. A simple Means of Proof. — Wind a stick 



194. How can it be proved that the atmosphere has weight ? 195. Give 
another proof that air has weight. 



90 PRINCIPLES OF CHEMISTRY. 

with cotton and press it to the bottom of a test-tube, 
containing enough water to moisten it thoroughly. 
It will be found difficult to withdraw the piston, 
jj The difficulty arises from the fact that the column 
of air which rests upon it, must be lifted at 
the same time. Having raised it a little way 
and released it, the piston flies with force to the 
bottom, owing to the weight of the same column 
of air. A common syringe closed at the bot- 
tom is very convenient for performing this ex- 
periment. 

197. Elastic Force of the Atmosphere. — Every 
cubic inch of air at the surface of the earth, may be 
likened to a hollow cube of india-rubber, which has 
been forcibly compressed into the space of a cubic 
inch.* If we suppose a cube of rubber, while 
thus compressed, to be confined in a strong metallic 
box, it would evidently exert an elastic force in all di- 
rections, equal to the force which compressed it. So 
the lower portions of air, which are kept compressed 
by the air above, exert elastic force. And it is better 
to regard the pressure of fifteen pounds on every square 
inch of the surface of the earth, as a consequence of 
the elastic force of the lower portions of air, rather 



196. Describe a simple means of proving that air has weight. 197. 
Whence does the air derive its elastic force ? 



* India rubber may be made to change its form by presssure but its cubical dimen- 
sions are no more compressible than water which is usually regarded as almost en- 
tirely inelastic. 



HEAT. 91 

than the direct effect of the weight of the whole air. 
The weight of the whole atmosphere produces the 
elastic force of the lower portions by compressing them, 
and the elastic force of the lower portions exerts the 
pressure. 

198. "Why the Pressure of the Air does not 
crush us. — If a thin glass vessel were turned upside 
down, and air-tight, upon a table, it would collapse but 
for the fact that it is filled with air, which, according 
to the last paragraph, has elastic force equal to that of 
the air without. So our bodies would collapse, but for 
the fact that our lungs, and all of the cavities of the 
body, are filled with air, possessing the same elastic 
force as the external air; a force which it had ac- 
quired by compression, before it was taken into our 
bodies. 

199. Quantity of "Water the Pressure of the Air 
will sustain. — If a tumbler is 
filled under water, and then lifted 
to the surface, as represented in fig- 
ure 38, it is well known that the 
water will not run out. The pres- 
sure of the atmosphere on the sur- 
face of the water outside, keeps the water forced up on 
the inside. 

Fill a tumbler with water and cover it with paper, 
and placing the hand upon it turn it bottom upward, 

198. Why are we not crushed by the pressure of the atmosphere ? 
199. What sustains the water in the inverted tumbler represented in the 
figure "i 




92 



PRINCIPLES OF CHEMISTRY. 




then if the hand is withdrawn the water will remain 
in the tumbler, being held there by 
the upward pressure of the atmos- 
phere as shown in the annexed 
figure. 

200. The effect would be the same 
if the tumbler were twice as tall, or 
if we suppose it lengthened into a 
tube thirty-three feet long. If a 
still longer tube were used, in the first experiment the 
level of the water inside, would never be more than 
thirty-three feet above the level outside. The 
remainder of the tube would be empty, as re- 
presented in figure 40. In other words, the 
pressure of the atmosphere will sustain a col- 
umn of water thirty-three feet high. "Water 
rises in a pump from this cause. 

201. Quantity of Mercury the Pressure 
of the Air can sustain. — In performing the 
experiment of the last paragraph with mercury, 
it will be found that the level within the tube 
will be thirty inches above the external level. 
In other words, the pressure of the atmosphere 
will sustain a column of mercury thirty inches 
high. This is because a column of mercury 
thirty inches high is just as heavy as a column of 
water thirty-three feet high. 




200. What quantity of water will the air sustain? 201. How many 
inches of mercury will the air sustain ? 



HEAT. 93 

202. If a long tube is used, there is, of course, an 
empty space above. This is called the Toricellian 
vacuum, from the fact that a vccuum was first pro- 
duced in this manner by an Italian philosopher, named 
Toricelli. It is not an absolute vacuum, a small portion 
of mercury being always present in the space in the 
form of transparent vapor. 

203. Boiling. — Thus far we have considered solely 
the formation of vapors from the surfaces of liquids. 
But where any liquid is heated up to a certain point, 
vapor forms in bubbles below its surface. This rapid 
formation of vapor below the surface of a liquid causing 
it to burst out with a gurgling noise is called boiling. 

204. Water begins to boil when it is heated up to 
212°; alcohol, at 173°; and ether, at 96°. As the 
proper temperature is first 4i 

reached at the bottom of the 
vessel, near the fire, the for- 
mation of bubbles begins 
there ; and as the surplus 
heat comes in below, they 
continue to be formed at 
this point. Every liquid 
has its own boiling point. 

205. Expansion in Boil- 
ing. — A cubic inch of water boiled in an open vessel, 
produces 1696 cubic inches of steam. A drop one-tenth 

202. Explain the Toricellian vacuum. 203. What is meant by the term 
boiling? 204. What is the boiling point of water? Of ether? Of 
alcohol? 205. How much steam does a cubic inch of water, alcohol, and 
ether respectively produce ? 




94 



PRINCIPLES OF CHEMISTRY. 



of an inch in diameter, would make enough to fill a 
sphere of the diameter of one and a fifth inches. A 
cubic inch of alcohol produces about 500 cubic inches of 
alcohol vapor; one of ether about 250. The ether 
vapor is most dense, that of alcohol next, and the steam 
least so. 

206. Disappearance of Heat in Boiling. — If a 
thermometer is held in boiling water, it indicates a 
temperature of 212° F. Continue the fire, and although 
heat constantly passes up into the water through the 
bottom of the vessel, it grows no hotter. The steam 
which is produced has also precisely the same tempera- 
ture. Neither water nor steam is 
hotter, although both have been con- 
stantly taking in heat. But the 
heat has not been without effect, 
any more than in the conversion of 
a solid into a liquid. It has com- 
bined with the liquid to form the 
steam. In this case, also, the heat 
which disappears is called latent 
heat. § 150. 

207. Eelation of pressure to 
boiling. — In order that a bubble of 
steam may form, it is necessary that a small portion of 
water, shall expand into a comparatively large portion 
of steam to form it. But the atmosphere is constantly 
pressing on the surface of the water, and acting through 




206. What is said of the disappearance of heat in boiling ? 207. How 
does pressure oppose boiling? 



HEAT. 95 

the water, in all parts of the vessel, to prevent any 
separation of particles or expansion, The case is simi- 
lar to that of the elastic cube before supposed, (197), 
which was forcibly compressed into a smaller space 
than it usually occupied. 

208. Heat overcomes Pressure. — But if we could 
by some means increase the elasticity of the elastic 
cube, it would expand and lift the iron. So, if we 
can in any way increase the tendency of the particles 
of water to separate, it will finally be strong enough to 
overcome the pressure of the atmosphere above and ef- 
fect separation. Heat has this effect. As the water be- 
comes hotter, the tendency of its particles to fly apart be- 
comes greater and greater, until, at last, it is sufficient 
to overcome the pressure which has before crowded them 
together, and a bubble of steam is formed. Others im- 
mediately follow, and boiling thus commences. This 
takes place at 212° Fahrenheit, which is therefore call- 
ed the lotting point of water. 

209. Effect of Height on Boiling. — At great ele- 
vations, the atmosphere is, in fact, lighter and there 
is less of it above us ; the consequence is that water 
boils on mountains at a lower temperature than in the 
valleys below. It is found, by careful observation, 
that an elevation of five hundred and fifty feet above 
the level of the sea, makes a difference of one degree 
in the boiling point. 

210. Measurement of Altitudes. — This fact once 

208. Explain how heat overcomes pressure. 209. What effect has 
height on boiling ? 210. How can the height of mountains he determined : 



96 PRINCIPLES OF CHEMISTRY. 

established, a tea-kettle and a thermometer are the 
only requisites for taking the height of a mountain. 
The summit being reached, the tea-kettle is boiled, and 
the heat of the water tested by the thermometer. If 
the mercury stands at 211°, it is known that the height 
is 550 feet; if at 210°, the height is 1100 feet; and at 
whatever point it stands, it is only necessary to multi- 
ply 550 by the number of degrees of depression of the 
mercury below 212°, to ascertain the elevation. On 
the top of Mont Blanc, water was observed by Sausure 
to boil at 184:°. This gives us the means of calculating 
very closely the height of that mountain. 

211. Effect of depth on Boiling. — In mines the 
atmosphere is heavier, and there is, beside, more of it 
above us, than at the surface of the earth. Water 
must, in consequence, be more highly heated before it 
will boil. 550 feet makes, as before, a difference of 
one degree. We are thus provided with a simple 
means of determining the depth of mines. Owing to 
various causes, the atmosphere at the same elevation is 
a little heavier some days than others, so that the height 
of a mountain or the depth of a mine, as thus meas- 
ured, would not be always precisely correct. 

212. Artificial change of Boiling Point. — It is 
obvious, from what has already been stated, that all it 
is necessary to do to change the boiling point, is to 
change the pressure of the atmosphere, on the surface 
of the water to be boiled. To produce this change of 

211. What effect has depth on boiling ? 212. How can the boiling; 
point of liquids be changed? 



HEAT. 97 

pressure, it is not necessary to ascend mountains, or to 
descend into mines ; it may be done by removing the 
atmosphere by artificial means. This would be done by 
attaching a tube, air-tight, to the mouth of a test-tube 
or flask and drawing off the air by means of an 
air pump. Cold water may thus be caused to 
boil. So by pumping more air into the flask, 
the pressure would be increased, and the boil- 
ing point elevated ; and by this means boiling 
water would be prevented from further boiling. 
The same effect will be produced by attempt- 
ing to boil water in a flask firmly closed by a 
cork. The steam first formed so increases the pressure 
that boiling can only be continued by rapidly increasing 
the temperature much above the ordinary boiling point. 
This subject is further considered in paragraph 216. 

213. Culinary Paradox. — Boil some water in a flask 
or test-tube, and then cork it tightly while steam 

is still issuing from its mouth. Though removed 
from the fire, the water will continue to boil. 
This will be best observed by inverting the flask or 
tube, as the bubbles of steam form more rapidly 
from the cork surface than from the glass. A 
few drops of cold water sprinkled on the tube 
will occasion a more violent ebullition ; while on 
the other hand, boiling water, or the application of 
flame, will cause the boiling to cease. 

214, Explanation. — The principle is the same as in 

213. Describe the culinary paradox. 214. Explain the principle of the 
culinary paradox. 

5 



98 PRINCIPLES OF CHEMISTRY. 

the experiment of paragraph 212. As the steam con- 
denses, by the cooling influence of the air, a partial 
vacuum is produced, with diminished pressure, which 
enables the water to boil with less heat. Cold water, 
by condensing the steam and removing the pressure 
more perfectly, increases the ebullition, while boiling 
water or flame renews the steam, and consequent pres- 
sure, and therefore checks boiling. 

215. Water Hammer. — The test-tube prepared as 
above, is a simple form of the " water hammer." If 
very thoroughly cooled, and then shaken with the kind 
of motion which would be required to make a bullet 
rise half way in the tube and fall again, the water 
will strike like lead on the bottom. It is because there 
is no air and but little vapor present to break its fall. 

216. Sugar Boiling. — When syrup is boiled down 
under the ordinary pressure of the atmosphere, it is apt 
to be brown or injured in flavor. By boiling it in a 
pan with an air-tight lid, and pumping off the air, and 
the vapor as fast as formed, boiling may be easily 
effected at a temperature as low as 150°. This method 
is put in practice by sugar boilers, and the disadvanta- 
ges above mentioned are thus avoided and a larger 
amount and better quality of sugar are obtained. 

Many vegetable juices and infusions used for medi- 
cines which would be injured by a high temperature, 
are boiled down, like sugar syrup, under diminished 
pressure. 

215. Describe the water hammer. 216. How may syrup be boiled be- 
low 212° F. ? 



HEAT. 99 

217. This method cannot be employed in cooking. 
The water might indeed be made to boil at 180°, but 
water boiling at this temperature would not have suffi- 
cient heat to cook our food like water boiling at 212°. 

218. Sixging of the Tea-Kettle. — -The 'singing 
sound which precedes boiling, is owing to the collapse 
of the first bubbles of steam, as they rise into the colder 
water above. The very first bubbles that form are not 
steam, but air which the heat expels. Steam bubbles 
are then formed, which rise a little way, and, being re- 
converted into water, contract, and finally collapse. If 
the heat is continued and the water made hotter, the 
next are able to rise further. Finally, when the water 
becomes as hot as the bubbles, they make their way 
through, and boiling is thus commenced. 

219. Steam Boilers. — The boiler is the vessel in 
which steam is formed. From the 

45 

boiler it passes to other parts of 
the apparatus to move the machine- 
ry. Steam boilers are of various 
forms, but are always made of great 
strength to resist the internal pres- 
sure to which they are subjected. 

220. The figure represents an ordinary steam boiler, 
with the pipe which conveys the steam to the engine. 
A safety-valve is also represented, which will be more 
fully explained in another paragraph. 



217, Can food be cooked by the same method ? 218. Explain the sing- 
ing of the tea-kettle. 219. What is a steam-boiler? 220. Explain the 
figure. 




100 PRINCIPLES OF CHEMISTRY. 

221. Elastic Force of Steam. — Under ordinary cir- 
cumstances, the elastic force of steam is obviously equal 
to the elastic force or pressure of the atmosphere. A 
man who rises from a chair with a fifty-six pound 
weight on his shoulder, must exert an extra muscular 
force, equivalent to fifty-six pounds, in rising ; and he 
must continue to exert it while he stands. So every 
bubble of steam must have an elastic force equal to 
that of the air which it lifts, or it cannot be formed 
under the pressure of the atmosphere, or continue to 
exist when once formed. 

222. Elastic Force, how increased. — As long as 
the vessel, in which steam is made, is open, the pressure 
is as stated in the last paragraph. But if the boiler is 
closed steam-tight, and the heat continued, more steam 
forms, and, crowding into the same space above the 
water increases the pressure. In other words, the space 
becomes filled with denser steam, of greater elastic 
force; and the force is finally sufficient to burst the 
boiler, unless it can find some vent. 

223. Increased Temperature accompanies In- 
creased Pressure. — Steam of high elastic force can 
only be made in a close vessel. But in proportion to 
the increase of elastic force, is the increase of pressure 
on the surface of the water. Therefore, the boiling 
point becomes higher and higher, or, in other words, 
the water has to grow constantly hotter, in order that 



221. How great is the elastic force of steam ? 222. How is the elastic 
force of steam increased ? 223. What accompanies increased pressure 
of steam ? 



HEAT. 101 

steam may form ; and as steam always has the temper- 
ature of the water with which it is in contact, the steam 
grows constantly hotter also. 

224. The exact Relation of Temperature to 
Pressure. — It is desirable to know the increase of 
pressure for each elevation of temperature. A steam 
boiler supplied with a barometer gauge and a thermo- 
meter affords the means of ascertaining this relation. 
Or it may be done by a very small boiler, made for the 
purpose. The barometer gauge is nothing more than a 
bent tube fitted into a boiler, open to the air at the top, 
and containing quicksilver in the lower part of the bend. 
We will suppose all the air to have 
been expelled from the boiler, the 
stop-cock through which it made its 
escape closed, and the whole interior 
to be filled with steam. As more 
steam is produced, pressure is in- 
creased, and the temperature of 
both water and steam rise, as before explained. 

225. "Where the temperature has reached 250°, it is 
found that the pressure of the steam, acting on the 
surface of the quicksilver, is sufficient to force and hold 
the latter thirty inches higher in one arm of the tube 
than in the other. But the steam with which the 
boiler was filled when the stop-cock was closed, exerted 
a pressure of fifteen pounds per square inch, just suffi- 



224. How can the exact relations of temperature to pressure be deter- 
mined ? 225. What pressure has steam at 250 ? at 275 ? at 294 ? How is 
this shown ? 




102 PRINCIPLES OF CHEMISTRY. 

cient to balance the pressure of the external air, and 
prevent its forcing the quicksilver before it and crowd- 
ing into the boiler through the tube. As before stated, 
when the thermometer reaches 250°, it is found that 
the denser steam will not only balance the atmosphere, 
but has force enough to lift the mercury thirty inches, 
which is equivalent to another atmosphere. Steam at 
250°, and in contact with water, is therefore said to 
exert a pressure of two atmospheres, or thirty pounds 
to the square inch. At 275° it has a pressure of three 
atmospheres ; and at 294° of four. 

226. All Yapor has Elastic Force. — 
The apparatus just described shows the pres- 
sure of steam at and above 212 degrees. But 
vapor of water has elastic force at all tempera- 
tures. This is best shown by passing a little 
water up into a Toricellian vacuum, and ob- 
serving the effect. The water is introduced 
by blowing it through a glass tube, one end of 
which is brought under the mouth of the in- 
verted tube. The drop rises and floats on the 
mercury, and as vapor forms at all temperatures, 
a portion of it is immediately converted into 
vapor. At the same time the level of the mer- 
cury is depressed. It is crowded down in opposition to 
the pressure of the air outside, by the elastic force of the 
vapor formed. For the sake of simplicity, the space 
above the mercury was supposed to be a vacuum, but 
the effect is the same if it is filled with air. For, as 

226. What is said of the elastic force of vapors at low temperatures ? 




HEAT. 



103 



48 



AB 



C D 



has been already shown, vapor is produced as well in air 
as in a vacuum, and with the same elastic force, though 
it is not formed so rapidly in air as in a vacuum. If 
the top of the tube is warmed, denser vapor is formed, 
possessing greater elastic force, and the mercury sinks 
lower, until at 212° the elastic force within, is equivalent 
to the pressure of the atmosphere without, and the 
mercur is pressed down to the external level. If in- 
stead of a drop of 
water a drop of al- 
cohol or ether is al- 
lowed to pass up 
into the barometer- 
tube the depression 
of the mercury is 
greater than when 
water is admitted. 
The figure shows 
at A, a barometer 
tube in which there 
is a perfect vacuum 
at the top, or as 
perfect a vacuum 
as can be formed 
with the mercurial 
barometer ; at b is 
a similar tube in 
which vapor of water is formed at the top ; at c the top 
of the tube contains vapor of alcohol, and at d is a simi- 
lar tube showing the depression caused by the formation 




104 PRINCIPLES OF CHEMISTRY. 

of vapor from a drop of ether passed up through 
the mercury. Here we see that vapor of alcohol has 
greater tension (or power of depressing the mercury) 
than vapor of water, and vapor of ether has still greater 
tension than vapor of alcohol. 

227. Barometer-Gattge. — The principle of the barom- 
eter-gauge has already been explained, (224.) A few 
words will be added here as to its use and construction. 
It is always desirable to know the pressure in a steam 
boiler, as an evidence of safety, and in order that the 
fires may be regulated accordingly, and no more fuel 
be consumed than is necessary. Sometimes the tube 
containing the quicksilver is of glass, and then the 
height of the mercury can be seen. In other cases it 
is made of iron, and the change of level of the quick- 
silver is indicated by a float. 

228. Other Steam Gauges. — A thermometer may 
be made to answer, perfectly, the purpose of a steam- 
gauge, as is evident from what has been said in para- 
graph 225. The advantage of such a gauge is, that it 
takes but little room ; its disadvantage, that it is liable 
to be broken. 

229. There is still another kind of gauge, in which 
the force of the steam operates on a metallic spring, 
which moves an index more or less, according to the 
pressure. The spring-gauge is commonly used in loco- 
motive boilers. 



227. Explain the construction and use of the barometer guage. 228. 
Explain the thermometer-guage. 229. Explain the principle of another 
guage. 



HEAT. 105 

230. Actual Pressure ik different Engines. — The 
actual pressure of steam, used in different forms of the 
steam engine, varies very widely. There are low and 
high pressure engines. In the former, steam of ten to 
thirty pounds effective pressure is used ; in the latter^ 
the pressure often reaches, and sometimes exceeds, 
seventy-five pounds. To measure the pressure, the 
steam gauge described in paragraph 227 would have to 
be five or six feet long. It is on account of this incon- 
venient length, that other gauges are often substi- 
tuted. 

231. By effective pressure, is meant the surplus over 
and above that which is necessary to counterbalance 
the pressure of the atmosphere, or that of the uncon- 
densed steam, on the opposite side of the piston. 

232. Safety- Valve. — The safety- 49 
valve is a contrivance by means of ^'■■,„„,„».,m,^ e 
which the steam finds vent through a 
hole in the boiler, whenever its force 
becomes too great for safety. A piece =Jj| 
of metal, shaped somewhat like a decanter stopper, fits 
into the hole above mentioned, and is loaded by a 
weight, which can be made greater or less at pleasure. 
As long as the steam has not too great pressure, the 
stopper continues in its place, and the boiler is as tight 
as if it had no such opening. When this pressure is 
exceeded, the valve is lifted, and steam escapes. The 

230. Explain the difference between high and lovr pressure engine -. 
231. What is meant by effective pressure ? 232. Explain and illu-1- t« 
the principle of the safety valve. 




106 PRINCIPLES OF CHEMISTRY. 

stopper, being loaded, falls back again, as soon as the 
pressure is relieved. 

233. The Steam Engine. — The power applied in the 
steam engine is the elastic force of steam. The figure 
represents a cylinder and close fitting piston, and tubes 
through which steam may be admitted, at pleasure, 
either above or below. When the valve in the lower 
tube is opened, the steam under pressure in 
the boiler, expands and enters the cylinder, 
lifting the piston. If the steam is next 
admitted above, it drives the piston back 
again, and the latter may thus be kept in 
constant motion, and made to move wheels, 
shafts, or other machinery. In the earlier 
forms of the steam engine a man or a boy 
was employed to open and shut the cocks to admit or 
shut off the steam at the right moment. This service 
was long since dispensed with and the machinery is so 
constructed as to open and shut the valves at the right 
moment by its own motion. The arrangement by which 
this is effected will be understood by inspecting figure 
51. At the top and bottom of the cylinders are open- 
ings called " ports" through which the steam enters 
and leaves the cylinders. On the side of the cylinder 
there is placed what is called a D-valve, which works in 
a box, and slides over a piece of metal which has three 
openings. This D-valve is shown at No. 3, and the 
metal face with its three openings over which the valve 

233. ExpLain the principle of the steam engine. 




HEAT. 



107 



slides is shown at No. 4. The upper and lower holes 
are seen to be connected by means of pipes with the 
top and bottom 
of the cylinder 
through which 
the steam passes 
to and fro. The 
middle hole is 
connected with 
a pipe through 
which the steam 
passes off into 
the air when 
it has done its 
work. In that 
part of the fig- 
ure marked £To. 
1, the valve is 
shown in such a 
position that the 
steam from the 
boiler, which 
enters the box 
in the direction 
of the arrow, 

passes below the no. 2. No. l. 

piston and forces it upwards. In No. 2 the steam from 
the boiler is passing to the top of the cylinder and is 
therefore pressing the piston downwards ; in both posi- 
tions that part of the cylinder which is shut off from 




108 PRINCIPLES OF CHEMISTRY. 

the steam-supply is losing its steam by the middle open- 
ing which is never closed by the D-valve. The piston- 
rod, c, is attached by the connecting-rod, Z, to the crank, 
hj attached to a shaft which moves any machinery re- 
quired. To the valve a rod, A, is fixed (Nos. 1 and 2,) 
and by means of another rod it is connected with a 
lever, p o, which is moved by a contrivance called an 
eccentric, m, attached to the shaft. The eccentric is a 
circular plate so attached to the shaft on one side of the 
center that it acts like a crank. If a pin is driven 
through a circular card at a little distance from the 
center and the card is turned around on the pin it will 
move like the eccentric of a steam-engine. Around the 
eccentric is a metallic ring connected with the rod, n, 
which is attached to the lever at o. "When the eccen- 
tric turns around with the shaft, it either pulls or pushes 
the lever, pp. In No. 1, it has forced o down and^p 
up ; and as p is connected with the D-valve that has 
been raised to the top of the box the steam is al- 
lowed to escape from the top of the cylinder into the 
open air. In 'No. 2, o has been raised and p has been 
depressed, thus allowing the steam to proceed to the top 
of the cylinder while it escapes into the air from the 
bottom. By means of this ingenious arrangement the 
engine supplies itself with steam and so works continu- 
ously without the necessity of any human assistance. 
The eccentric can be so arranged on the shaft and 
the D-valve so adjusted as to cut off the supply of steam 
before the piston is driven to the extremity of the 
cylinder. As steam expands with great force it fills 



HEAT. 109 

the cylinder by its expansion and a great saving of 
steam and heat is thus effected. In this arrangement 
of the valves there is a short interval when the steam 
does not enter either end of the cylinder. 

234. High Pressure Engine. — The engine, here 
described, is called the high pressure engine. The 
steam which moves it, must evidently have elastic force 
greater than that of the atmosphere, or it cannot ex- 
pand and drive out the waste steam, in opposition to 
the elastic force of the air. Steam of much higher pres- 
sure is used in such engines, than in those to be next 
described, and hence their name. 

235. Low Pressure Engine. — The same figure will 
answer to illustrate the low pressure engine. The dif- 
ference is, that the steam which has been used is not 
driven out, but disposed of, on the spot, by converting 
it into water. The advantage of this will be readily 
perceived. Suppose the space above the piston to be 
full of steam. A jet of water is made to play into it 
and condense the steam, and thereby produce a vacuum. 
"When, immediately afterward, steam is admitted below 
the piston, the latter has nothing on the other side to 
drive out, and consequently rises more easily. As 
less force is required, steam of lower pressure may be 
used, with a corresponding economy of the heat and 
fuel required in its production. 

236. The Condenser. — In steam engines, as now 



234. W T hat is a high pressure engine ? 235. Explain the principle of 
the low pressure engine. 236. What is the use and object of the con- 
denser ? 



110 PRINCIPLES OF CHEMISTRY. 

made, the water used to condense the steam does not 
come into the cylinder itself, but into a side vessel, 
called the condenser. The steam expands into this ves- 
sel, and is condensed, producing a vacuum in the cylin- 
der itself, as effectually as if the water were there in- 
troduced. The object of this modification is to avoid 
cooling the cylinder and thereby diminish the effect of 
the steam subsequently entering from the boiler. This 
engine is called the low pressure engine, from the fact 
that steam of lower pressure may be employed to move 
it than with the engine previously described. It may, 
indeed, be made to run with vapor formed below 212°, 
instead of steam. But in practice, steam of from ten 
to thirty pounds effective pressure is employed. 

237. Original Steam Engine. — In the original form 
of the steam engine, the pressure of the atmosphere, 
instead of steam, was applied on one side of the piston, 
and it therefore received the name of the atmospheric 
engine. Suppose the cylinder in the last figure to be 
open at the top, and the piston at its full height. On 
condensing the steam below it, the piston would evi- 
dently sink, in consequence of the pressure of the 
atmosphere. By thus employing steam pressure on 
one side, and atmospheric pressure on the other, a con- 
stant motion would be realized. But the effective 
power would evidently be less than in the low pressure 
engine, because part of it would have to be expended 
each time in lifting the piston, in opposition to the pres- 
sure of the atmosphere. 

237. Explain the original low pressure engine ? 



HEAT. Ill 

238. A test tube containing a few drops of water and 
provided with a wooded piston suffices to illustrate the 
source of power in the steam engine. On alternately 
heating and cooling the tube motion of the piston is ef- 
fected. 

239. The Mechanical Equivalent of Heat. — The 
mechanical equivalent of heat, or in other words the 
amount of force required to produce a given amount of 
heat, (and which can in its turn be produced by the 
same amount of heat), has been carefully determined by 
experiment. The result is the same whether the con- 
version of force into heat is effected by the falling of 
weights, the friction of metals, the agitation of liquids, 
or the hammering of solids. A pound weight falling 
through 772 feet will develop heat enough on collision 
with the earth to raise a pound of water one degree 
Fahrenheit in temperature. 

Conversely, this same amount of heat applied me- 
chanically (in the production of steam or otherwise) is 
competent to raise a pound weight 772 feet, or 772 
pounds one foot. The amounts of force and heat thus 
indicated are therefore equivalent. The term foot- 
pound (equivalent to foot-raised-jpound) has been intro- 
duced to express the force required to lift one pound to 
the height of a foot. " The quantity of heat required 
to raise the temperature of water one degree being taken 
as a standard, 772 foot-pounds constitute what is called 
the mechanical equivalent of heat" 

238. How may the steam engine be simply iUustrated ? 239. How is the 
mechanical equivalent of heat determined ? What is taken as the standard ? 



112 PRINCIPLES OF CHEMISTRY. 

240. Conversion of Yapors into Liquids. — If a 
vapor, in any way, loses its latent lieat, it at once be- 
comes liquid. If, for example, steam be led into a cool 
pipe, the metal abstracts the latent heat, and the steam 
becomes water. At the same time, the heated pipe im- 
parts warmth to the air around it. 

241. Heating Houses by Steam. — Houses are thus 
heated, by steam pipes passing through the various 
apartments. The pipes abstract the heat, and give it 
out again to the air of the house. The steam thus 
converted into water, runs back into the boiler to be 
reheated, and to start again on its journey. As long 
as heat is supplied, the water continues its service as 
a carrier of heat. The great amount of latent heat 
which steam contains renders it an excellent medium 
for conveying heat to any apartment where it is wanted. 
In the most approved steam heaters steam of low pres- 
sure is used. 

"When buildings are heated by steam conveyed in 
pipes from a boiler used with high pressure the tem- 
perature often rises to 300° or 400° ; and if the pipes 
are connected with wood-work the w T ood after a time 
becomes so thoroughly dried, that even the heat of the 
steam-pipes sets fire to the wood. Many accidents 
have occurred from this cause in buildings heated by 
steam. When steam at low pressure only is employed 
for heating buildings there is less danger of setting fire 



240. How are vapors converted into liquids ? Example. 241. How are 
houses heated by steam ? What accidents sometimes occur when build- 
ings are heated by steam ? 



HEAT. 113 

to the wood-work than when hot-air furnaces are em- 
ployed. 

242. Water heated by Steam. — When steam is 
led into water, the effect is the same as on leading it 
into a cold pipe. The water abstracts its latent heat, 
and becomes hot, while the steam itself becomes addi- 
tional hot water. Water in different parts of a room, 
or even of a large manufacturing establishment, may 
thus be made to boil by one fire ; steam being led into 
it, by long pipes, from a single boiler. 

243. Proof that Boilixg is effected by Latest 
Heat. — ~No amount of boiling water, if poured into 
cold water, will make it boil. But steam no hotter 
than the boiling water, if led into cold water, will have 
this effect. Now, as both the hot water and the steam 
were the same in respect to sensible heat, if the steam 
effects what the water does not, it is evident that it 
must do it by hidden, or latent heat. It is only latent 
heat which the steam loses, for it becomes itself con- 
verted into equally hot water. 

244. Quantity of Latent Heat. — A pint of water 
will make enough steam to fill a globe nearly four feet 
in diameter. If this amount of steam could suddenly 
become a pint of water, and be prevented from flying 
off into steam again, it would become red hot. The 
latent heat of the steam would have raised the temper- 
ature from 212° to 1212° — a thousand degrees. Steam 



242. How is water heated by steam? 243. Prove that boiling is 
effected by latent heat. 244. How much latent heat does steam con- 
tain ? 



Hi 



PRINCIPLES OF CHEMISTRY. 



is therefore said to contain 1000 degrees of latent heat. 
According to Regnault the latent heat of steam varies 
at different temperatures. At 212° it is 966.6°. At 
32° the latent heat of vapor of water is 1092.6°. 

245. Sum of Sensible and Latent Heat nearly 
Constant. — Yapor formed by the heat of summer, oc- 
cupies more space, and contains more heat, in a latent 
condition than is contained in steam. And it is found 
to be true that very nearly in proportion as vapor or 
steam feels cool, or indicates a lower temperature to the 
thermometer, it contains more latent heat to the same 
quantity of water. The sum of the sensible and latent 
heat at the ordinary pressure of the atmosphere is ap- 
proximately the same — about 1178°. 

246. Economy in Evaporation. — It follows that 
evaporation at low temperatures, such as is practiced 
sometimes in sugar-houses, has no advantage of econo- 
my. The vapor that passes off, carries with it less sen- 
sible heat, but enough more latent heat in proportion, 

to make up the difference. 

247. Distillation. 

— Distillation con- 
sists in converting 
a liquid into vapor, 
and recondensing the 
vapor. The appara- 
tus commonly em- 




245. What is the relation of sensible to latent heat ? 246. Why is 
there no economy in evaporating at low temperatures ? 247. Describe 
the process of distillation. 



HEAT 



115 



ployed in the laboratory for distillation, consists of a retort 
and a receiver, as represented in figure 52. The receiver 
is kept cool by the constant application of cold water. 
In Liebig's apparatus, figure 53, for the same purpose, the 
vapors are made to pass from the retort or flask through a 

53 




54 



long inclined tube, a h. The latter is inclosed in a second 
tube, A B, which is constantly supplied with cold water 
by the funnel,/, which extends higher than the end, a, 
of the larger tube, and escapes by the tube cL A more 
perfect condensation is thus effected. The simple ap- 
paratus shown in figure 54 
also suffices for illustra- 
tion. Water being boiled 



in the test-tube, the steam 
condenses in the cooler 
vial. If the latter is cov- 
ered with wet paper, the 
condensation is more per- 
fect. 

248. Object of Distillation. — The object of distil- 
lation is commonly to purify, or, in other words to 




248. What is the object of distillation ? Give examples. 



116 PRINCIPLES OF CHEMISTRY. 

separate the liquid distilled, from otlier substances with 
which it may be mixed. Tims, sea water is distilled to 
separate the pure water from salt. The water becomes 
steam, and is condensed as pure water, while the salt 
remains behind. So alcohol is distilled, or converted 
into vapor, and recondensed, to separate it from water, 
and the various refuse matters which are mixed with it 
after fermentation. But the separation is not perfect, 
for, although alcohol is more volatile, and distills more 
rapidly, a portion of water always distills w^ith it. Dis- 
tilled liquors, therefore, uniformly contain a certain 
proportion of water. 



CHAPTER IV. 

MAGNETISM JkJSnD ELECTEICITY, 

249. Native Magnets. — The native magnet, or lode- 
stone, is a mineral w^hich has the remarkable property 
of attracting metallic iron to itself, and of taking north 
and south direction, w T hen suspended and free to move. 
Particles of iron brought near, rush toward it, and re- 
main attached to its surface, without any visible cause. 
It exerts this attractive force just as well through wood, 
stone, or any other material, as through the air. 

249. What properties has the native magnet ? 




MAGNETISM AND ELECTRICITY. 117 

250. Artificial Magnet. — The same properties may 
be imparted to a piece of steel, by a process to be here- 
after described. Such a piece of steel thereby becomes 
itself a magnet. Magnets are often made 
of a shape approaching that of a horse-shoe, 
the two poles being brought near each 
other. A piece of soft iron, called an arma- 
ture, is placed across the end to prevent the 
loss of magnetic power, which is found otherwise to 
occur. 

251. Magnetic Keedle. — If a steel bar be made 
into a magnet, and then balanced on a pivot, it will 
turn, until one end points north and the other south. 
That which moves toward the north is 
called the north pole, and the other end 
the south pole. A small bar thus bal- 
anced is called a magnetic needle, and is 
the essential part of the mariner's com- 
pass. 

252. Attraction of Magnets for each other. — 
The law of attraction between magnets is, that unlike 
poles attract, and like poles repel. The north pole of 
one magnet, therefore, attracts, and is attracted by the 
south pole of another. 

253. Why the Magnetic Needle points North. — 
The tendency of the north pole of the magnetic needle 
to turn north, and the other pole south, may be ae- 



250. Describe an artificial magnet. 251. What is the magnetic needle ? 
252. How do the poles of magnets act on each other ? 253. Why does 
the magnetic needle point north ? 




118 



PRINCIPLES OF CHEMISTRY. 




counted for by the supposition of an enormous magnet 
running through the earth, with powerfully attracting 
poles in each hemisphere. This may be illustrated by 

suspending a small 
magnetic needle, s n, 
over a globe nine 
or ten inches in di- 
ameter in the axis of 
which a steel mag- 
net, IN" S, is placed. 
When the axis of 
the magnet is hori- 
zontal the needle, n s, will arrange itself as shown in 
figure 57. This represents the condition of things 
at the equator. Figure 58 shows the relation of the 
earth and the needle as it approaches the north pole. 

In order that the pole of the supposed magnet in the 
northern hemisphere of the earth may attract the pole 
of the magnetic needle which points to the north, we 
must suppose it endowed with that kind of polarity 
found in that pole of the needle which points to the 
south, that is, we must suppose it to be a south pole, 
and for a similar reason we must suppose the pole in 
the southern hemisphere to be a north pole. This in- 
consistency may be avoided, and the poles of the sup- 
posed terrestrial magnet named according to their 
geographical position, if we regard what is called the 
north pole of the needle, as endowed with austral or 
southern magnetism, and the south pole with northern 
or boreal magnetism. This view is, in fact, adopted in 



MAGNETISM AXD ELECTRICITY. 119 

all writings on magnetism. The received theory is 
hereafter given. 

254. Induced Magnetism. — When a piece of iron is 
brought near to a magnet, the iron receives magnetism, 
by induction, and becomes itself, temporarily, a mag- 
net. If approached to the south pole, its adjacent end 
acquires north, and the remote one south, polar- 
ity, and mutual attraction results. By virtue of % 
its acquired or induced magnetism it will at- 
tract another piece of iron, as is represented in 
the figure, and affect it in all respects similarly. 
From the second key, another smaller one may 
be suspended, and from this another, and so on. 
This arrangement of the keys affords an illustra- 
tion of the probable inner constitution of a mag- 
net. The atoms of which it is composed, themselves 
possess polarity and are arranged with their opposite 
poles adjacent. Induction is the communication of 
this polar arrangement. 

If the keys or pieces of iron attached to the magnet, 
as shown in the figure, are tested by the approach of a 
magnetic needle the entire series acts only as an ex- 
tension, or prolongation of the pole of the original 
magnet, the parts marked X and S in the figure both 
have the same action towards the needle used as a test. 
This is because the feeble north (X) polarity induced in 
the end of the key in contact with the south (S) pole of 
the magnet has its influence upon the testing needle 



254. Explain induction of magnetism in soft iron. 



120 PRINCIPLES OF CHEMISTRY. 

overbalanced by the greater intensity of south polarity 
in the magnet itself. In the same manner if a bar 
magnet of feeble intensity has its north pole placed in 
contact with the south pole of a very powerful magnet, 
the magnetism of the feeble magnet will be masked 
and it will appear, as in the case of the keys, to be 
merely an extension of the south pole of the power- 
ful magnet, but when removed from the influence 
of the larger magnet it will again manifest its own 
polarity. 

255. Diamagnetism. — If a needle of iron be hung by 
a thread, between the poles of a horse-shoe magnet, it 
immediately turns, so that one of its ends points to the 
north pole, and the other to the south. This is also a 
consequence of induced magnetism, as explained in the 
preceding paragraph. The metal nickel, oxygen gas, 
and many other substances, both solid, liquid and 
gaseous, are similarly attracted by the poles of a mag- 
net, though in a much less degree. All bodies which 
are not attracted are repelled, and, if suspended between 
the poles, turn so as to bring their extremities as far 
away from the poles as is possible. The former class 
are called magnetic, and the latter diamagnetic bodies. 
To show the phenomena of attraction and repulsion 
with gases and liquids, the materials are inclosed in 
tubes or bulbs. In the case of most substances, except- 
ing iron, these effects can only be attained by means of 
powerful magnets and delicate apparatus. 

255. What is said of diamagnetism 



MAGNETISM AND ELECTRICITY. 121 



Electricity. 

256. Frictional Electricity. — If a glass tube is 
rubbed with silk, it will afterward attract to itself fila- 
ments of the silk, as a magnet attracts iron. Or, if the 
knuckle be approached to the tube, a spark may be 
drawn from it. These phenomena are called electrical. 
Both glass and silk are said to be electrically excited. 
The same experiment may be made with a stick of seal- 
ing-wax, a roll of sulphur and a variety of other sub- 
stances. 

257. Two Kinds of Electricity. — Suspend a small 
piece of tissue paper by a fiber of silk, and bring near 
to it the glass tube previously excited as above direct- 
ed, the paper will be first attracted to the tube and 
then as strongly repelled. While thus repelled by 
glass, bring towards it a stick of sealing wax excited in 
the same manner, and the paper will be immediately 
attracted by the wax and again repelled, but it will 
afterwards be again attracted by the glass tube. It is 
thus evident that by friction of the glass and of the 
wax two similar but opposite forces are developed. In 
order to distinguish these two opposite kinds of electri- 
city, that which is obtained from glass has been termed 
vitreous, or positive electricity ; while that derived from 
the wax is called negative or resinous electricity. The 
suspended paper is called an electroscope , or test for 
electricity, 

256. What is frictional electricity ? 257. How is it shown that there 
are two kinds of electricity? 

6 



122 



PRINCIPLES OF CHEMISTRY. 




258. The coexistence of the two kinds of electricity 
in the same object may be illustrated by the elasticity 

of an ordinary spring as shown 
at S, figure 60. "When the spring 
is not extended it may represent 
the body in its ordinary condi- 
tion when no electricity is mani- 
fested. If one end of the spring 
is fastened to a pin, P, and a 
weight, W, is attached to the 
other end by a cord passing 
over a pulley, it will appear to 
be stretched by one force only. 
But this is not in reality the case. For if, instead of 
fastening one end to the pin, we attach to it another 
weight Y, just equal to W, thus obviously introducing 
a second force, the strain upon the spring will not be 
changed. The case of electrical excitement is ana- 
logous ; when one kind only appears to be developed 
by friction or any other means, a careful examination 
will always detect an equal amount of the opposite 
kind of electricity. 

259. Theory. — According to the view commonly 
entertained of the class of phenomena described on 
the preceding page, all bodies contain two electrical 
fluids in a state of combination. When glass is rub- 
bed with silk, the positive fluid accumulates in the 
glass and the negative in the silk. When sealing 

258. How can the action of two kinds of electricity be illustrated ? 
259. State the theory of electricity. 



MAGNETISM AND ELECTRICITY. 123 

wax is rubbed with silk the positive electricity accumu- 
lates in the silk and the negative in the sealing-wax. 
The positive sustains the same relation to the negative, 
that the north polarity of a magnet does to the south ; 
and, in consequence of the difference of the separated 
fluids, the two bodies containing them attract like op- 
posite poles of a magnet. It is also true, that similarly 
electrified bodies repel like similar poles of magnets. 
Slips of gold leaf, attached to a conducting rod, fly 
apart when the rod is touched by an electrified body. 

260. The human body may also be electrically exci- 
ted, so as to yield a spark, by rapid sliding over a Brus- 
sels carpet. Gas may be lighted by the spark from the 
finger when the body is thus charged with electricity. 
The gas in certain manufactories is instantaneously 
lighted throughout the whole establishment by electric 
city developed by the friction of the machinery. 

261. Conduction of Electricity. — Like heat or calo- 
ric, electricity may be conducted from one body to 
another. Thus, if a piece of metal be electrically ex- 
cited, or, in other words, charged with a quantity of 
either the positive or negative fluid, another piece of 
metal will immediately become so on connecting it with 
the first by a metallic wire. The connection being 
formed, it will attract or repel filaments of silk or other 
material, precisely as the first one does. The fluid is 
supposed to flow from one piece of metal to the other, 
through the wire, and we therefore speak of a current 

260. Illustrate by examples. 261. Explain the conduction of elec- 
tricity. 



124 



PRINCIPLES OF CHEMISTRY. 



of electricity. But it is not necessary to suppose tb at any 
material substance is actually transmitted any more than 
in the case of light and heat before considered. § 288. 
262. The Leyden Jar. — This instrument shown in 
figure 61 is designed to collect and preserve electricity 
for the purpose of experiments. It consists of a glass 
jar coated inside and outside with tinfoil for about three- 
fourths of its height. 
A brass knob at the 
top is supported up- 
on a rod or wire pass- 
ing through the cork 
and touching the 
coating of tinfoil on 
the inside of the jar. 
After the Leyden 
jar has been charged 
with electricity a strong spark is emitted whenever a 
conductor makes a connection between the knob and 
the outer coating. 

263. Yoltaic Electricity. — This term 
is applied to electricity which is set in 
motion by chemical action and was adopt- 
ed in honor of Yolta, who discovered 
this kind of electricity. It is found that 
electricity is developed when two metals 
are placed in contact with each other, and 
with an acid at the same time, as is represented in the 
figure. The metals must be such that the acid will act 




X^ 



62 




262. Describe the Leyden jar. 263. What is Voltaic electricity ? 



MAGNETISM AND ELECTRICITY. 125 

on one of them. Zinc and copper being used, the for- 
mer is dissolved, and the current flows continuously 
in the direction indicated by the arrows. This appara- 
tus is the simplest form of the Yoltaic battery. 

264. Electrodes. — For convenience in certain ex- 
periments, it is customary to attach platinum wires, to 
the exterior portions of the metallic slips. These are 
called electrodes. The wire connected with the copper 
forms the positive electrode, and the one attached to 
the zinc, the negative, because the current of electricity 
passes from the copper over the wire to the zinc. 

265. Platinum wire is chosen, because there is fre- 
quent occasion to immerse the electrodes in corrosive 
liquids, and this metal, for the most part, withstands 
their action. For many experiments, it is found best 
to flatten the ends of the wires forming the electrodes, 
so as to produce a larger surface. The same object 
may also be effected by terminating them with strips 
or plates of platinum. 

266. Electrical Condition of Atoms. — All atoms 
of matter are regarded as originally charged wdth either 
positive or negative electricity. Hydrogen and the 
metals are electro-positive ; oxygen, chlorine, and cyan- 
ogen, and other substances to be described hereafter, 
are negative. A molecule* of water is made up of a 
positive atom of hydrogen, and a negative atom of 

264. What is an electrode ? 265. Why is platinum used for electrodes ? 
266. What is the electrical condition of atoms? 



* The term atom, and molecule, are synonymous. But " molecule" is limited, 
in the present work, to the particle of a compound. 



126 PRINCIPLES OF CHEMISTRY. 

oxygen; hydrochloric acid, of positive hydrogen and 
negative chlorine ; oxide of silver, of positive silver 
and negative oxygen. The figure, in which + repre- 
03 sents positive and — negative, may represent a 
/qyg^ molecule of either of the compounds named. 
267 Quantity of Electricity. — The quan- 
tity of electricity thus combined or neutralized, in almost 
all kinds of matter, is enormous. Faraday has stated 
that a drop of water, contains more than is discharged 
in the most violent flash of lightning. 

268. Decomposition of Water. — If the electrodes 
are immersed in water, as repre- 
sented in the figure, the water is 
decomposed, and separated into its 
elements, oxygen and hydrogen 
gases ; one of which escapes at the 
positive and the other at the nega- 
tive electrode* The properties of 
these elements and the method of 

collecting and testing them, will be described w r hen we 
come to speak of the chemical composition of water. 

269. It is to be observed that positive hydrogen is 
liberated at the negative pole, as if the latter had a 
power analogous to that of the magnet for iron, to draw 
the hydrogen out of the water, in which it exists com- 
bined. On the other hand, negative oxygen is libera- 

2C7. Wliat quantity of electricity is contained in water? 2G8. Describe 
the decomposition of water. 269. Why does hydrogen appear at the 
negative pole ? 




* In making the experiment the compound circuit (290) is to be employed. 




. MAGNETISM AND ELECTICITY. 127 

ted at the positive pole, as though the latter had the 
same attractive power for oxygen. 

270. Theory of the Decomposition of "Watee. — 
It is a remarkable circumstance, in the decomposition 
just described, that it continues to occur even when 
the electrodes are quite widely separated from each 
other. Now, a molecule of water is extremely small, 
and cannot occupy the space be- 
tween the electrodes, if they are 
separated to any considerable ex- 
tent. The space must be occu- 
pied by many such particles, 
which, for the sake of definite- 
ness, we will conceive of as ar- 
ranged in straight lines, between the two electrodes. 
The circles in the figure, inscribed H and O, represent 
one of these lines of molecules. The difficulty now 
arises, to account for the fact, that when the hydrogen 
is liberated at the negative pole, the oxygen, combined 
with it a moment before, is not also liberated at the 
same point. The view to be taken of it is as follows : 
that as soon as the atom of oxygen loses its hydrogen, 
it combines with the hydrogen of the next molecule of 
water. The oxygen of this second one being thereby 
liberated, combines with the hydrogen of the next ; 
and this decomposition and recomposition continues 
throughout the series. The end of the series being 
reached, the last oxygen atom escapes in the form of 

270. Give the theory of the decomposition of water. 



128 



PRINCIPLES OF CHEMISTRY. 



gas. The action being simultaneous throughout the 
series, this evolution occurs at the instant that the hy- 
drogen is set at liberty at the negative electrode. It is, 
therefore, quite as proper to giVe the explanation of 
the difficulty first stated, by beginning with the libera- 
tion of oxygen at the positive electrode. We then sup- 
pose the hydrogen to combine with the oxygen of the 
next molecule of water in the series, and so on to the 
negative electrode, where hydrogen is evolved. The 
action is, in fact, as before stated, simultaneous. 

271. Decomposition of a Salt. — The decomposition 
effected by the voltaic current may be more strikingly 
illustrated by introducing the electrodes into a dilute 
solution of sal-ammoniac, previously 
colored by litmus, or red cabbage. 
Chlorine is liberated at the positive 
pole, and bleaches the solution in its 
vicinity, while ammonia is evolved 
with hydrogen, at the negative pole, 
and changes the color of the solution from blue to red. 
That of the cabbage is changed by the same means, 
from red to green. By employing a glass box with two 
compartments, such as is represented in the figure, the 
two portions of the liquid may be kept distinct. It is 
essential, for reasons that will be understood from the 
preceding paragraph, that there be an unbroken chain 
of molecules of the electrolyte^ or substance to be de- 
composed, between the electrodes. This is effected by 




271. Describe the decomposition of a salt. 



MAGNETISM AND ELECTRICITY. 129 

making the partition quite loose, and keeping it in its 
place by strips of paper, placed along the edge. All 
the communication that is essential, then takes place 
through the pores of the paper, while the partition at 
the same time prevents the mixing of the contents of 
the separate cells. The same object may be accom- 
plished by the employment of two tea-cups, holding the 
liquids, and connected by moistened lamp-wick; a 
larger pile, and a longer time, is in this case required 
to effect the decomposition. The glass box may be 
made according to the directions given in paragraph 
33 for making a prism. 

272. Deposition of Metals. — The metals are elec- 
tro-positive. Oxygen, chlorine, etc., on the other hand, 
are negative. If, therefore, oxides, chlorides, or cyan- 
ides of the metals are subjected to the action of the 
electrodes, they are decomposed, while the metal goes to 
the negative, and the oxygen, chlorine, or cyanogen, to 
the positive pole. But the metals, when separated from 
their combinations, being solid bodies, cannot escape. 
They collect on the negative electrode, instead. If 
this be attached to a brass spoon or fork, or any other 
object it is desired to plate, the spoon becomes itself the 
electrode, and the metal is deposited upon it as long as 
the action of the battery continues. At the same time, 
the oxygen, or other negative element, goes to the posi- 
tive electrode, generally corroding it, instead of passing 
off as gas. 



272. Explain the deposition of metals by galvanism. 

6* 



130 PRINCIPLES OF CHEMISTRY. 

273. Silvering Apparatus. — The requirements for 
electro-silvering or gilding, are first a battery of some- 
what different form from that already described, though 
precisely the same in principle ; second, an acid to ex- 
cite it ; and third, a solution containing gold or silver. 
These will be described in turn. 

6 ^ 274. A convenient form of 

^^^2k the apparatus is represented in 

^ ^^ ^S£^ /g g=jiilg | the figure, and may be prepared 
IK $lff H ' from sheet zinc and copper in a 

^Wli"l ^ ^^^ llllfc ^ ew rainutes. It consists of a 
^== EE ^=^-^ =r : bent strip of the former metal, 
with a strip of copper fastened between the two por- 
tions. The metals should be within an eighth of an 
inch of each other, but without contact. To secure this 
they are tied together with thread, bits of wood or cot- 
ton cloth being previously interposed. Copper wires 
being attached to the zinc and copper, as represented 
in the figure, the apparatus is placed in a common 
tumbler, and the battery is complete. 

275. Before combining the battery as above described, 
it is best to wash the zinc with soap and water, and 
afterward with dilute sulphuric acid, and then to im- 
merse it for half a minute or so in a solution of nitrate 
of mercury. By this process, the zinc acquires a thin 
film of quicksilver, which afterward protects it from the 
action of the acid used to excite the battery, excepting 
when the circuit is completed. When the battery is in 

273. What apparatus is required for electro-silvering? 274. Explain 
(he figure. 275. How and why is the zinc coated with quicksilver. 



MAGNETISM AND ELECTRICITY, 131 

operation, it also has the effect of making the action 
more equal and constant. It is then to be again wash- 
ed, and newly immersed in the acid solution. This solu- 
tion is prepared by dissolving quicksilver, of the bulk 
of two peas, in nitric acid, and pouring the clear liquid 
into a tumbler of water. 

276. The exciting Acid. — The exciting liquid is 
dilute sulphuric acid, consisting of one part oil of vit- 
riol, to ten parts of water. The acid is mixed with the 
proper quantity of water, and set aside to cool. 

277. The Silvering Solution. — To make half a 
pint of the solution, a dime is placed in a test-tube and 
dissolved in nitric acid, the solution being diluted with 
water. Muriatic acid is then added, which precipitates 
the silver, in the form of a white curd. This is allowed 
to settle, and the green liquid, which contains the cop- 
per of the coin, is poured off. "Water is again added, 
and the curd allowed to settle ; this cleansing process is 
several times repeated. The test-tube is then half filled 
with water, and heated, and bits of cyanide of potas- 
sium added, until a transparent solution is obtained. 

278. A solution for gilding is prepared by drying a 
solution of gold at a moderate heat, and dissolving it 
in cyanide of potassium, as above described. The pro- 
cess for gilding is in all respects the same as that for 
the deposition of silver. 

279. The Process. — The battery and silvering solu- 

276. How is the exciting acid prepared ? 277. How is the silvering so- 
lution prepared ? 278. How is the solution for gilding prepared ? 279. 
How is the silvering process conducted ? 



132 PRINCIPLES OF CHEMISTRY. 

tion being prepared, the copper coin, or other object to 
be silvered, is cleansed with potash, rubbed with chalk 
or rotten-stone, and then attached to the wire proceed- 
ing from the zinc. A silver coin is fastened to the 
other wire, and immersed in the silvering solution; 
acid is then added to excite the battery, and the object 
to be silvered is lastly immersed. It should be hung 
face to face with the silver coin, and quite near to it, 
the two being kept in their places by blocks placed 
across the tumbler, as represented in figure 69. The 
coin will receive a perceptible coating within a few 
minutes, and will be more thickly covered, according to 
the time of immersion. The deposition is hastened by 
keeping the solution moderately warm. This is espe- 
cially advantageous in the commencement of the pro- 
cess. The newly plated surface is without lustre, and 
requires burnishing after removal from the solution. 

280. Object of the Silver Coin. — The piece of 
silver is attached to the positive wire, to maintain the 
strength of the solution. It is eaten away and dis- 
solved as fast as silver is deposited on the objects con- 
nected with the negative wire. The reason of this is, 
that the cyanogen of the solution, when it goes to the 
positive pole, as before explained, combines with silver, 
forming new cyanide of silver, which dissolves and 
mixes with the rest. Thus, the strength of the solution 
is always maintained. The coin is attached to the 
negative wire, by flattening the latter, laying it on the 

280. What is the object of the silver coin? 



MAGNETISM AND ELECTRICITY. 133 

back of the coin, and covering the whole with sealing 
wax ; the coin and wire should be previously slightly 
warmed, and the wax used at a moderate heat, so that 
it shall not run between the wire and the coin, and pre- 
vent their perfect contact. 

281. Copying of Medals. — If it is desired to copy 
the face of a medal or a coin, the same apparatus suffi- 
ces. The reverse and edges of the coin are very slightly 
oiled, to prevent the adhesion of the copy about to be 
made. It is then placed in the solution. The metal 
deposits upon it, copying perfectly every elevation and 
depression. When the crust is sufficiently thick, which 
will be after the lapse of twelve hours, the coin, with 
its shell of metal, is removed, and the whole process 
repeated with the mold. The deposit which now 
forms in the shell, is an exact copy of the face of the 
original coin. Molds are also made by stamping the 
coin into soft metal, and using the impression thus pro- 
duced instead of the copper shell. Copper plates, for 
engravings, may be copied so perfectly by the first 
method, as to be fully equal to the original. 

282. Copying Wood Cuts. — A mold of the wood 
cut is first made by pressing it into wax ; but as the 
wax is not a good conductor, it will not itself receive a 
negative character from the negative wire of the bat- 
tery, and will not take positive metal from the solution. 
This difficulty is obviated by covering the wax mold 
with a fine powder of plumbago or black lead, which 
has good conducting power. 

281. How are medals copied ? 282. How are wood cuts copied ? 



134 PRINCIPLES OF CHEMISTRY. 

283. This process is very extensively practiced. 
Where a large number of cuts of the same kind are 
wanted, as for example, to print labels for dry goods, 
only one engraving on wood is made, and numerous 
copies are taken by the above process, which is much 
less costly. 

284. Heating Effects of the Current. — If the 
electrodes are connected while the battery is in action, 
the wire becomes heated more or less strongly, accord- 
ing to the size of the plates. If the plates are very 
large, the wire melts, even though it be of platinum, 
the most infusible of metals. Gold may even be con- 
verted into vapor by the same means. Carbon, sup- 
posed a few years since to be entirely infusible, may 
be also superficially fused, and even volatilized between 
the electrodes. It condenses again at a little distance, 
in the form of microscopic crystals. Imperfect dia- 
monds have been thus artificially produced. With 
such a battery as has been described the elevation of 
temperature would be scarcely perceptible. 

285. The Electric Light. — If the current be allowed 
to pass between two points of prepared charcoal, an 
exceedingly intense light is produced, accompanied by 
great heat. Charcoal is employed because it is compa- 
ratively infusible, because the solid particles torn off 
from one of the points have the power of becoming in- 
tensely luminous at the high temperature produced by 



283. In what cases is the process practiced ? 284. Describe the heating 
effect of the current. 285. How is the electric light produced ? 



MAGNETISM AND ELECTRICITY. 135 

reason of the low conducting power. A metallic wire, 
under the same circumstances, would melt, or if too 
large to undergo fusion, would allow the current to 
flow readily through it, without that detention which 
is essential to the production of the above effects, in 
their highest degree. 

286. If the charcoal points be withdrawn from each 
other, a splendid electric flame is produced between 
them. This flame is not the result of combustion, for 
the charcoal is extremely dense, and wastes away but 
slowly. It is purely electric. Metals melt in it, and 
are dissipated in vapor. A large battery is requisite 
for the production of either the light or flame. In ex- 
perimenting with the compound battery, a slight spark 
will be observed, on separating the electrodes. 

287. Source of Yoltaic Electricity. — Having con- 
sidered the effects of the Voltaic current in previous 
paragraphs, the student is now better prepared to un- 
derstand its origin. Our explanation relates especially 
to the simple form of battery already described. For 
other cases it is essentially the same. The origin of the 
current is to be found in the chemical action, induced 
by that electrical condition of the atoms of the metals 
and the acid which results from their contact. This 
will be the more readily comprehended if w^e consider 
first the case of a single metal and acid, and see why 
they will not suffice to produce a current. Suppose a 
curved bar of pure zinc Z to be immersed at its two 

287. Why will not an acid and one metal suffice ? 



136 



PRINCIPLES OF CHEMISTRY. 




ends in hydrochloric acid. The metal becomes by mere 
contact positively electrified at the points which are in 
contact with the acid and negatively electrified in the 
portion which is more remote. The liquid also be- 
comes electrically polarized, and 
in obedience to the polarizing in- 
fluence, its molecules turn their 
negative or chloric atoms toward 
the zinc. But in this form of 
the experiment no communica- 
tion existing between the nega- 
tive part of the zinc and the posi- 
tively electrified atoms of hydrogen, no change ensues 
beyond the production of this state of electric tension. 
288. Let us next suppose the half of the zinc on the 
left to be removed and a piece 
of platinum P to be substituted 
and brought into contact with 
the acid, but not as yet with the 
remaining portion of the zinc. 
The platinum is at once polar- 
ized by induction from the po- 
larized liquid ; the portion in 
contact with the acid becomes 
negatively, and the more remote portion positively, 
electrified. But in this case, as in the former, the cir- 
cuit still remaining uncompleted no change ensues be- 
yond the state of electrical tension before described. 




8. How do two metals and an acid act ? 



MAGNETISM AND ELECTRICITY. 



137 



Let us finally suppose that the outer extremities of the 
zinc and platinum are brought into contact and the cir- 
cuit completed. Communication being thus establish- 
ed the opposite electrical conditions of these portions 
of the metals mutually neutralize each other. A simi- 
lar act of equilibrium takes place at the same instant 
throughout the whole circuit. The zinc, which is posi- 
tive where it is in contact with the acid, combines with 
the negative atom of chlorine which is adjacent ; the 
hydrogen thus liberated seizes upon the chlorine of the 
molecule lying next to it in the series ; the hydrogen 
of this second molecule combines with the chlorine of 
the next and a similar action occurs throughout the 
chain. The last atom of hydrogen being incapable of 
combination with the platinum transfers its positive 
electricity to that metal and itself escapes as a gas. 

"With each escaping atom of hydrogen a new wave 
is added to the current. Fig. 70 il- 
lustrates the same subject in essen- 
tially the same manner. It is not 
to be supposed that any material 
substance is actually transmitted in 
the passage of the so-called current. 
What really occurs is a progressive 
alternation of the polar condition of 
the atoms which cannot in the present state of science 
be more accurately defined. 

289. A Salt employed as Excitant. — It is not essen- 




ls material substance transmitted in the current ? 289. Explain how a 
battery can be excited by a salt. 



PRINCIPLES OF CHEMISTRY. 



tial, that an acid should be used as the exciting liquid 
in the Yoltaic circuit. A metallic salt is sometimes 
employed. This may be best illustrated, by supposing 
chloride of copper to be employed instead of hydro- 
chloric acid, which is chloride of hydrogen. The chlor- 
ine goes to the zinc, as in the previous case, and the 
copper of the salt, to the strip of copper, placed in the 
solution. Being a solid, it remains there, and encrusts 
the copper, instead of being evolved, as in the case of 
hydrogen. , 

290. The Compound Yoltaic Circuit. — For the sake 
of simplicity the foregoing decompositions have been 
described as the effect of the current generated by'a 
single pair of plates. Several couples employed in con- 
nection are in general required, their size and number 
being varied according to the special object in view. 
The connection may be made as shown in figure 71. 

71 




There will in this case be no increase in the quantity 
of the current over that which may be obtained from a 
single pair of the same size. But its intensity or capa- 
city of overcoming resistance, offered in a greater or 
less degree by all conductors and in all decompositions, 
is greatly enhanced. Such an arrangement constitutes 

290. What is said of the compound circuit ? 



MAGNETISM AND ELECTRICITY. 



139 



a compound Voltaic circuit. Or, secondly, the plates 
may be united as in Figure 72. This arrangement has 



72 




73 



the same effect as the enlargement of the dimensions 
of a single pair. The quantity of the current is thus 
increased. 

291. The Yoltaic Pile.— The first form of Voltaic 
battery eyer produced is represented in 
the figure, and is called the Voltaic pile, 
from the name of its inventor. It consists 
of a succession of discs of zinc, copper 
and cloth, moistened with acid, alternat- 
ing with each other, as represented in the 
figure. Each series forms a simple bat- 
tery, and the whole pile is a compound 
battery, essentially the same as that be- 
fore described. Wires to serre as electrodes are to be 
attached to the extreme copper and zinc. 

292. The enlarged form of the Voltaic pile repre- 
sented in the next figure will be found a most efficient 
apparatus for effecting decomposition. It is composed 
of sixteen plates of each metal, each having a surface of 




291. Describe the Voltaic pile. 292. WTiat is said of the enlarged Vol- 
taic pile ? 



140 PRINCIPLES OF CHEMISTRY. 

twelve inches square. The zinc should be amalga- 
mated, as before explained. Flannel, or any similar 
material may be employed to separate the plates. 
With this piece of apparatus, the spark is readily 
obtained, and slight shocks may be taken by 
bringing the two hands into 
74. contact at the same moment 

with the top and bottom of the 
pile. On terminating the elec- 
trodes with fine iron wire, and 
frequently uniting and separat- 
ing them, scintillations of the 
burning metal may also be readily produced. By in- 
creasing the number of the plates still more striking 
effects are obtained. With a pile consisting of six or 
eight plates a foot square, platinum wire connecting 
the electrodes may be readily fused. Such a battery is 
also more effectual in the electro-magnetic experiments 
which follow. 

298. Different Kinds of Batteries. — There are 
different kinds of Yoltaic batteries, but the principle 
in all is the same. Two of the forms in most common 
use are described in the Appendix. Smee's battery is 
especially recommended to the student, for its cheap- 
ness, simplicity, and efficiency. It is very similar, as 
will be seen, to the simple one which has been already 
described. 

294. Magnetic Properties of the Current. — If 

293. What is said of the different kinds of batteries ? 294. Describe the 
magnetic properties of the Voltaic current. 



MAGNETISM AND ELECTRICITY, 



141 



the wire connecting the zinc and copper of the Yoltaic 
battery be wound in a spiral, as represented in the fig- 
ure, the coil, or helix, as it is 75 
termed, becomes possessed of mag- 
netic properties. Like a magnet, 
it attracts iron, and other magnets, and according to 
the same laws. 

295. The suspended Bar. — A rod of iron brought 
near one of the extremities of the coil, is not only at- 
tracted, but actually lifted up into the centre of the coil, 
where it remains suspended without contact, or 76 
visible support, as long as the battery continues 
in action. Science has thus realized the fable of 
Mahomet's coffin, which was said to have been 
miraculously suspended in the air. The helix, 
for this and similar experiments, is wound closer 
than is represented in the figure, and is com- 
posed of several layers of wire. A powerful bat- 
tery is also essential to success in this experi- 
ment. 

298. Polarity of the Coil. — That such a coil has 
polarity, may be proved, precisely as 
with a magnet. One end of it attracts 
the north pole of a magnet, and is 
therefore a south pole. The other end 
attracts the south pole of a magnetic 
needle, and is therefore, itself, a north 
pole. But the direction in which the 



11 




295. How may a rod of iron be suspended in the air ? 296. What is the 
action of a single wire on magnetic coil ? 



142 PRINCIPLES OF CHEMISTRY. 

current moves around in the helix, determines which 
shall be north, and which south. As the current is re- 
presented to move in the first of the two coils in the 
figure, the upper end of the coil is north, and the lower 
end south. If it is made to move in the other direc- 
tion, as in the second figure, the poles are reversed. 

297. Consequent Motion of a Suspended Coil. — 
To obtain motion of the coil itself, as a consequence of 
its magnetism, it is necessary to suspend it ; and in or- 
der to suspend it with perfect freedom of motion, it is 

necessary to suspend the bat- 
tery with it. Such a sus- 
pended coil and battery is re- 
presented in the figure. In 
preparing it, the wire is 
wound forty or fifty times 
around a test-tube, (which is afterward removed,) and 
copper and zinc plates then attached to the ends. The 
plates are tied together with several layers of paper be- 
tween them, then dipped in acid, and the apparatus 
carefully suspended by an untwisted silk fibre. The 
acid absorbed by the paper, suffices to maintain for 
some time the action of the battery. On approaching 
a magnet to either pole of the suspended coil, it is at- 
tracted or repelled precisely as if it were a magnet. 
Instead of suspending the apparatus by a thread, it may 
be floated on acidulated water, by means of a cork, and 
submitted to the same experiment. In this construc- 
tion, the wires proceeding from the end of the coil, pass 




297. How may we obtain motion of the coil itself? 



MAGNETISM AXD ELECTRICITY. 143 

through the cork, before connecting with the metallic 
plates. The first described method of suspension is re- 
garded as the best. 

238. The Coil a Magnetic Keedle. — On floating 
a coil with extreme delicacy upon water, and protecting 
it from all currents of air and water, it assumes north 
and south direction, and becomes, in fact, a magnetic 
needle. This can only be accomplished by means of a 
light glass cup, blown for the especial purpose, and pro- 
longed into a cone below, to give it steadiness in the 
water. This cup is filled with dilute acid, in which the 
plates are immersed, and is then floated in a larger 
vessel. 

299. Mutual Action of Coils. — Two helices, or 
coils, such as are described in the last paragraph, float- 
ing near each other, repel or attract, precisely as if they 
were magnets, according as like or ^ 9 

unlike poles are brought together. n 
They finally attach themselves to ^ 
each other in the position repre- ^ f^**-* ^ 

sented in the figure, lying parallel and with opposite 
poles in contact. In this position, it will be observed, 
that at the point of contact, the currents are moving in 
the same direction. The attraction of the unlike poles, 
may be regarded, then, as a consequence of the attrac- 
tion of like currents. For it is found to be universally 
true, that currents moving in the same general direc- 



298. How may the coil be converted into a magnetic needle ? 299. 
Describe the mutual action of magnetic coils. 




144 PRINCIPLES OF CHEMISTRY. 

tion, attract each other, while those moving in opposite 
directions, repel. 

300. Mutual Action of Coil and Magnet. — If a 
floating magnet be substituted for one of the coils, in 
the above experiment, the result is not in the least af- 
fected. They act towards each other precisely as if 
so both were magnets, or both coils. 

301. Action of a single Wire on a Coil. — 
A single wire, carrying a current, acts on a 
floating coil in the same manner. Stretched 
above it, as indicated in the figure, the north 
pole of the coil will move to the right. The 
motion is such as to bring adjacent currents, in 
the wire, and in the coil, to coincide in direc- 
tion. 

302. Polarity of the Coil imparted to Iron. — A 
bar of soft iron placed in the coil, becomes itself mag- 
netic, and receives the name of electro-magnet. 
It should be wound with several layers of con- 
tinuous wire, the latter being covered with cot- 
ton, to prevent any lateral passage of the cur- 
rent. The horse-shoe shape, in which the poles 
are brought around near to each other, is the 
more common. The power of such magnets 
continues only while the current is passing. 
Electro-magnets have been constructed capable of lift- 
ing a ton, or even more. They are sometimes employed 



300. What is the mutual action of a coil and magnet ? 301. What is 
the action of single wire on a magnetic coil ? 302. What effect has the 
magnetic coil upon metals ? 




MAGNETISM AND ELECTRICITY. 145 

in dressing iron ores, to separate, by their attraction, 
the workable ore from the refuse earth with which it is 
mixed. A steel bar introduced into the helix while the 
current is passing, becomes permanently magnetic. 
Permanent magnets are now commonly made in this 
manner. 

303. Permanent Magnetism of Steel. — It appears, 
from the last paragraph, that a bar of soft iron is a 
magnet, as long as an electrical current circulates 
around it. But the steel, if once magnetic, remains so 
permanently. This is accounted for, by supposing that 
the current, in the wire, excites a current in the surface 
of the steel itself, which continues to flow, without in- 
terruption, after the wire is reinoyed* 82 

304. Action of a single TTire on a Magnet. 
— A wire, carrying a current in the direction ^ 
shown in the figure, acts on a magnet, precisely 
as on a floating coil (301). The magnetic needle 
may therefore be employed to detect the pas- r]3 
sage of a Voltaic current. An instrument con- 
structed on this plan is called a galvanometer. 

305. Electrical Theory of Magnetism. — 
According to this theory, all magnetism, including that 
of the lode-stone, the magnetic needle, and that of the 
earth itself, is a consequence of the circulation of elec- 
trical currents. In the earth, such currents are known 
to be excited, and kept in motion, by the sun, heating 



303. What effect has tlie magnetic coil upon steel ? 304, What is the 
action of a single wire on a magnet ? 305, Explain the electrical theory 
of magnetism? 

7 



1 



146 



PRINCIPLES OF CHEMISTRY. 



in turn successive portions of its surface. They flow 
from east to west, making of the earth, as it were, an 
immense coil, or helix. In magnets they are also in 
constant circulation, the direction being dependent on 
the position in which the magnet is held. In the case 
of a magnet whose north pole is directed north, the 
direction is from west to east across the upper surface, 
and of course, in the contrary direction on the under 
side. The earth acts on a magnet, or a floating coil, 
as one helix acts on another. The north and south 
direction of the magnetic needle is a consequence of 
this action. 

306. The Theory Illustrated. — In illustration of 
this theory, let a globe be coiled with a wire, carrying 
a current, as indicated in the figure. Let the current 
flow from east to west through the coil. A small mag- 
netic needle placed at differ- 
ent points on the surface of 
the globe, however the posi- 
tion of the latter may be 
changed, will always point 
to its north pole. It is un- 
derstood, in this experiment, 
that the current is strong 
enough to overcome the in- 
fluence of the earth itself on 
the magnet. A freely movable coil through which a 
current was passing, would, in this case also, act pre- 
cisely like a magnet. 




306. Explain the figure. 



MAGNETISM AND ELECTRICITY. 147 

307. Magnetic Telegraph. — The explanation of 
the mechanism of the magnetic telegraph belongs to 
Natural Philosophy. The principle of its operation 
may be here given. It has already been stated, that a 
piece of soft iron becomes a magnet, when a current of 
electricity circulates in a coil surrounding it. Now, 
suppose the two ends of such a coil, situated in a dis- 
tant city, to be made long enough to reach a battery in 
the place where the reader resides, and to be stretched 
along over posts, and connected with the poles of the 
battery. The current occupies no perceptible time in 
its passage. Therefore, as soon as the battery is set in 
operation, it circulates through the whole extent of the 
wire, and, of course, through the coil in the distant 
city. The piece of iron which it incloses is made a 
magnet, and will immediately lift its armature. If the 
current is stopped, the piece of iron ceases to be a mag- 
net, and drops its armature. But the operator at the 
battery can send or stop the current at will, by simply 
disconnecting one of the wires, and thereby lift or let 
fall the armature a hundred or a thousand miles off, as 
often as he pleases. He can have an understanding, 
also, with the person in the distant city, who sees the 
motion of the armature, as to what it shall mean. One 
lift may indicate the letter A ; two, lifts, the letter B ; 
and so on. Words may be similarly spelled out, and it 
thus becomes possible to communicate ideas by electri- 
city. If these lifts of the armature can be made to 

307. Explain the principle of the magnetic telegraph ? 



148 PRINCIPLES OF CHEMISTRY. 

record themselves on a slip of paper, the further ad- 
vantage of writing at the distant station is gained. 
And this is precisely what is realized in Morse's tele- 
graph, and more particularly described in all recent 
works on Natural Philosophy. 

308. The Earth used as a Conductor. — It would 
seem requisite to extend both ends of the wire forming 
the coil through all the intervening distance, and then 
to connect them with the opposite poles of the battery ; 
but it is found, in practice, that one is sufficient, and 
that all the middle portion of the second wire may be 
dispensed with. The remaining ends, one connected 
with the helix, and the other with the battery, being 
made to terminate in large plates, and buried in the 
ground, the earth between them is found to take the 
place of the second wire, and complete the circuit. 

309. Applications of the Telegraph. — There are 
many applications of the telegraph besides the one of 
transmitting intelligence to distant places. In the 
city of Boston, an alarm of fire is instantaneously com- 
municated throughout the city, and the bells are rung 
by telegraphic apparatus. 

In Marseilles, France, a single clock is made by sim- 
ilar means to indicate the time on dials, placed in the 
street lamps of the city. Electro-magnetic apparatus 
has also been employed with the most remarkable suc- 
cess in increasing the dispatch and accuracy of astro- 
nomical observations ; making it possible to accomplish 

308. What is said of the earth as a conductor ? 309. Mention some 
remarkable applications of the telegraph. 



MAGNETISM AND ELECTRICITY. 149 

during a single night in the study of the heavens, what 
formerly cost a month of labor. 

310. Physiological Effect of Voltaic Electric- 
ity. — The nerves of animals are extremely susceptible 
to the influence of Yoltaic electricity. The apparatus 
represented in the figure, which consists of strips of 
zinc and copper, three inches in length, separated by a 
cork, is sufficient to produce con- 84 

vulsive twitching in the legs of 
a frog or toad. A larger appa- 
ratus produces more decided effects. The legs are to be 
employed, with a portion of the back bone attached, 
which is grasped by the sharpened extremities of the 
Galvanic tweezers. As often as the circuit is comple- 
ted, by bringing the other extremities into contact, by 
the pressure of the fingers, the legs are observed to 
twitch, as if they were still possessed of life. The leg 
of a grasshopper, held in its thickest part, may also be 
employed in the experiment. In both these cases, the 
moisture of the flesh or skin is the exciting fluid of the 
Voltaic couple. 

311. Correlation of Forces. — The intimate relation 
that exists between Mechanical Force, Heat, Light, Elec- 
tricity, Magnetism and Chemical Affinity, has already 
been abundantly illustrated. We have found, for ex- 
ample, that chemical action in the cell of a Voltaic bat- 
tery produces a current of electricity, and that this may 
be converted, in turn, into Heat, Light, Magnetism or 

310. Describe the physiological effects of Voltaic electricity. 311. What 
is said of the correlation of forces ? 



150 PRINCIPLES OF CHEMISTRY. 

Mechanical Force. Or, beginning at the other end of 
the series, we have seen how Mechanical Force may be 
changed into Heat, and this in turn into Electricity, 
Magnetism and Light. This conversion is always ef- 
fected in proportions which are definite and constant. 

312. Conservation of Force. — Further, the quantity 
of any force thus produced is reconvertible into the 
original force, without loss, excepting such as is due to 
imperfections of method. And even this portion, which 
seems to be wasted, takes the form of some other of the 
correlated forces. The heat which is expended in rais- 
ing a weight to a given height will be reproduced when 
the same weight is allowed to fall to the earth. The 
force of affinity which effects the solution of zinc in the 
battery may be reproduced, with only such loss as is 
above indicated, by decomposing a solution of zinc and 
thus isolating a portion of metal and acid by means of 
the current which the original act of combination has 
excited. 

Force in nature is indestructible. It may appear at 
one time as heat pouring upon the earth from the sun, 
again as electricity generated by his rays ; it may com- 
mence its course as affinity residing in some atom, then 
take the form of a Yoltaic current traveling a wire and 
again appear as magnetism lifting an armature, but it 
is never destroyed or in any degree diminished. The 
forces of nature like the atoms of matter are indestruct- 
ible except by the Power which called them into being. 

312. What is said of the convertibility of forces ? Conservation of 
force ? 



PART II. 

LAWS OF COMBINATION, 



CHAPTER I. 



313. Number of Elements. — The number of ele- 
ments, or simple substances, at present known is sixty- 
two. Only thirty-five of these are of sufficient import- 
ance to be considered in this work. The rest are of 
rare occurrence, and are found in comparatively small 
quantity. 

314. Subdivision of the Elements. — The elements 
may be divided into metals and metalloids, or non- 
metallic substances. They are thus divided in the 
table given on page 154. Hydrogen and oxygen be- 
long to the class of non-metallic substances, but are 
placed by themselves, for reasons which will appear in 
the sequel. 

315. Atomic Constitution. — All of the elementary 
substances, whether they be solids, liquids, or gases, are 
regarded as made up of minute atoms, as explained in 
Chapter I. All of the atoms of the same substance are 
alike in every respect. 

313. What is the number of the elements ? 314. How are the elements 
subdivided ? 315. Of what are the elementary substances made up ? 



152 PRINCIPLES OF CHEMISTRY. 

316. Combination by Atoms. — When combination 
takes place between portions of any two elementary 
substances, it may be regarded as consisting in the at- 
traction and juxtaposition of their individual molecules. 
Thus, when zinc tarnishes in the air, each of the atoms 
which form the surface of the zinc, takes to itself an 
atom of oxygen from the air, and the whole surface be- 
comes covered with molecules of oxide of zinc. In the 
same manner, sulphuric acid is made up of compound 
molecules, each one of which consists of an atom of sul- 
phur, and three of oxygen. 

317. Atomic "Weights. — Although the atoms of all 
substances are too small to be separately seen, chemists 
believe not only that they have evidence of their exist- 
ence, but that they know their relative weight. The 
relative weight of the atoms of a few of the elementary 
substances, as compared with the hydrogen atom, 
which is the lightest of all, is given i*i the following 
table, as nearly as it can be given in whole numbers. 

318. It is to be borne in mind that the table does not 
undertake to tell the absolute weight of the hydrogen 
atom, or of any other atom. This is not known. It 
only informs us that whatever may be the weight of the 
hydrogen atom, that of oxygen weighs eight times, that 
of sulphur sixteen times, and that of carbon six times 
as much : and so on of the other elements. 

319. Chemical Symbols. — To facilitate the statement 



316. How does combination take place ? 317. What is known of the 
weight of atoms? 318. How is the table which follows to be under- 
stood ? 319. What are symbols ? 



LAWS OF COMBINATION. 153 

and explanation of chemical charges certain abbrevia- 
tions of the names of elements are employed, called 
symbols. The abbreviation or symbol representing any 
substance consists of the first letter or letters of the 
name by which the substance is known to men of sci- 
ence. This is not always the common name, thus O 
stands for oxygen, S for sulphur, and C for carbon, cfec, 
while K stands for potassium, called Kaliurn by chem- 
ists, and N" stands for sodium or natrium, and Ag for 
silver or argenhtm. 

320. Explanation of the Symbols. — The symbols 
may best be regarded by the student as standing for 
single particles of the several substances. Thus, N", CI, 
P, K, S, Ca, indicate respectively single atoms of Ni- 
trogen, Chlorine, Phosphorus, Potassium, Sodium, and 
Calcium, and the numbers in the next column of the 
table indicate the relative weight of the atoms. In the 
case of compounds, the symbols also show their composi- 
tion. Thus, X0 5 stands for a single molecule of Citric 
acid, and, besides, indicates, as represented in the figure, 
that every such molecule is a compound mole- 85 
cule consisting of one atom of nitrogen, and (||p 
five atoms of oxygen. 

321. Again, KO stands for a single molecule of 
Potassa, and indicates that it is a compound con- -^ 
sisting of one atom of potassium and one of oxy- 
gen. Such a compound of two elements is called a 
"binary compound. 

320. What do the symbols stand for? Give examples. 321. What 
does KO indicate ? 



154 



PRINCIPLES OF CHEMISTRY. 



TABLE OF SOME OF THE MORE IMPORTANT ELEMENTS 
AND THEIR COMPOUNDS 

METALLOIDS. 



Name. 
Hydrogen, . 
Oxygen, — 



Symbol. Atomic weight. 
...H 1 

....0 8 



METALLOIDS. 

Name. Symbol. 

Nitrogen, N 

Chlorine,. .CI 

Phosphorus, P 

Sulphur, S 

Carbon C 



14 
35 
32 
16 
6 



METALS. 

Name. Symbol. 

Potassium, (Kalium.) K 
Sodium, (Natrium.) Na 

Calcium, Ca 

Magnesium, Mg 

Barium, Ba 



39 
23 
20 
12 



Metalloids with Oxygen form 
ACIDS. 

Nitric Acid, N0 5 

Chloric Acid, C10 5 

Phosphoric Acid, PO5 

Sulphuric Acid, SO3 

Carbonic Acid, C0 2 



Metals with Oxygen form 
OXIDES or BASES. 

Potassa, .KO 

Soda, NaO 

Baryta, BaO 

Calcia, CaO 

MgO 



Acids with Bases form 
SALTS. 



Nitrate of Potassa, KO,N"0 5 

Nitrate of Soda, NaO,N0 5 

Nitrate of Baryta, BaO,N0 5 

Nitrate of Calcia CaO,N0 5 

Nitrate of Magnesia, . . . .MgO,NOs 



Sulphate of Potassa,.. .KD,S0 3 

Sulphate of Soda, NaO,S0 3 

Sulphate of Baryta, . . .BaO,S0 3 

Sulphate of Calcia CaO,S0 3 

Sulphate of Magnesia. .MgO,S0 3 



Each of the other acids forms its class of salts. There are other 
classes of acids, to be hereafter mentioned, which contain no oxygen. 



What do metalloids form with oxygen ? Give some examples. 
What do metals form with oxygen ? Give some examples. 
What do acids form with bases ? Name all of the salts which may he formed 
from the acids and bases above mentioned. 



LAWS OF COMBINATION. 155 

322. In the same manner KO,lSr0 5 stands for a single 
molecule of Nitrate of Potassa, and indicates tliat 
every such molecule is a compound, made up of two 
other compound molecules, one of nitric acid, and 
another of potassa. Such a compound, of two . JSL. 
binary compounds, is called a ternary com- ( M^ \ 
pound. The symbols may, indeed, be regarded '• -SS 

as standing for larger quantities, in the same relative pro- 
portion ; but it is an assistance in understanding chemi- 
cal phenomena, to regard them as has been suggested. 

323. Atomic Weights of Compounds. — The relative 
weight of the atoms of simple substances is given in 
the table. With the help of these and the symbols, the 
relative weight of the molecules of compounds is easily 
calculated. Thus, the symbol of nitric acid, being 
N0 5 , we know that 54 must be the weight of the 
molecule of nitric acid. For the symbol informs us 
that it is made up of a single atom of nitrogen (14) 
and five atoms of oxygen, (40). The weight of a mole- 
cule of potassa is 47, its symbol (KO) informing us, 
that it is made up of one atom of potassium, (39), and 
one atom of oxygen, (8). 

324. Calculations of Weights from Symbols. — 
From the symbols of compounds, the relative weight 
of their components may be calculated. N0 5 , being 
the symbol of nitric acid, we know, as above shown, 
that the weight of its least particle is 54, and that this 



322. What does KO, NO5 indicate? 323. How are atomic weights of 
compounds determined? 324. How are absolute weights calculated 
from symbols ? 



156 PRINCIPLES OF CHEMISTRY. 

weight is made up of nitrogen, 14, and oxygen, 40. 
As a larger quantity is composed of precisely such 
particles, the relative weight of the constituents must 
be the same. Fifty-four pounds of nitric acid, there- 
fore, contain 14 pounds of nitrogen, and 40 pounds of 
oxygen. In the same manner, from the symbol KO, 
with the help of the table of atomic weights, we ascer- 
tain that 47 pounds of potassa contain 39 pounds of 
potassium, and 8 pounds of oxygen. CaO,S0 3 , is the 
symbol of Sulphate of Lime or Gypsum. Adding the 
atomic weight of its constituents, we have 68 as the 
sum. Sixty-eight pounds of sulphate of lime, there- 
fore, contain 20 pounds of calcium, 16 pounds of sul- 
phur, and 32 pounds of oxygen. 

325. Definite Proportions. — The composition of the 
same substance is always the same. "When hydrogen 
and oxygen unite, in the proportion of one of the for- 
mer to eight of the latter, they form water, (HO). . If 
an excess of either element is employed, it remains 
uncombined. When they unite in a different propor- 
tion, as they do in another process, they form not water 
nor a modification of water, but an entirely new and 
distinct substance, viz., peroxide of hydrogen, (H0 2 ), 
whose composition is also uniformly the same. So 
nitrogen combines w T ith oxygen, in each one of the 
proportions indicated by the symbols, NX), N"0 2 , 
N0 3 , N0 4 , N0 5 , in each case forming a new sub- 
stance. 

325. Illustrate the law of definite proportions. 



LAWS OF COMBINATION. 157 

326. Multiple Proportions. — As combination al- 
ways takes place by whole atoms, and never by frac- 
tions, it is # evident that whenever it occurs in more than 
one proportion, the others must be multiples of the first 
proportion or atomic weight. Thus the proportions, 
by weight, in which oxygen unites with nitrogen, are 
8, 16, 24, 32, 40. In other than such exact propor- 
tions, combination never takes place. 

327. Chemical Equivalents. — It has already been 
shown that the atomic weights express the proportions 
in which substances combine with e&ch other. It also 
expresses, as would be naturally inferred, the propor- 
tions in which they replace each other, whenever such 
replacement occurs. Thus, chlorine sometimes expels 
and replaces oxygen in chemical compounds. 'When- 
ever this takes place, 35 parts of the former, by weight, 
are required to replace 8 parts of oxygen. These num- 
bers, therefore, express chemical equivalents of the two 
substances, and in general, a table of atomic weights, is 
also a table of chemical equivalents. So, when sul- 
phuric acid expels nitric acid from any of its salts, it 
replaces it in the proportion of 40, to 54. The atom 
of sulphuric acid is the equivalent of that of nitric acid 
in another sense. It has precisely an equivalent effect 
in neutralizing the base with which this acid may be 
combined. 

328. The composition of a mixture, is sometimes ex. 

326. What is the law of multiple proportions ? Give examples. 327. 
What is a chemical equivalent ? Give an example. 328. How is compo- 
sition expressed by equivalents ? 



158 PRINCIPLES OF CHEMISTRY. 

pressed by equivalents. Gunpowder, for example, may 
be described as containing one equivalent of sulphur, 
one of nitre, and three of carbon. This signifies that it 
is composed of 16 parts of sulphur, 101 of nitre, and 
18 of carbon, as may be ascertained, by calculation, 
from the table of atomic weights. 

329. Names of Oxides. — It will be observed from 
the table, that the oxide of potassium is called potassa ; 
the oxide of sodium, soda, and so on, each oxide having 
a special name, derived from the name of the metal. 
The oxides of most of the other metals, not mentioned 
in the table, have no special names, but are called 
oxide of iron, oxide of lead, oxide of zinc, &c. 

330. Names of Salts. — Compounds formed by the 
union of oxides and acids are called salts. In naming 
the salts of the oxides the term oxide is generally 
omitted for the sake of brevity. Thus, we say, nitrate 
of iron, sulphate of iron, phosphate of iron, instead of 
nitrate of oxide of iron, sulphate of oxide of iron, etc. 

331. Formation of Oxides. — Most of the oxides of 
the table are immediately formed as soon as their re- 
spective metals and oxygen come together. Thus, out 
of silvery potassium and transparent oxygen, white 
potassa is instantaneously produced. But, it is more 
commonly necessary to heat a metal with oxygen, to 
form its oxide. The oxides are also called bases. 
They are further considered in Part III. 

329. How are the oxides named ? Give examples. 330. What are salts, 
and how are they named ? Give examples. 331. How are oxides formed ? 
Give an example. 



LAWS OF COMBINATION. 159 

332. As oxygen forms oxides with metals, so 
chlorine, bromine, iodine, fluorine and sulphur form, 
respectively, chlorides, bromides, iodides, fluor- 
ides, and sulphides. The latter are also called sul- 
phurets. 

333. Formation of Acids. — Simple contact of a 
metalloid, and oxygen, is not generally sufficient to 
produce an acid. Heat is one among the additional 
means employed. Thus, carbon or charcoal, heated 
with oxygen, or in air which contains it, is immediately 
converted into carbonic acid. Different acids are some- 
times formed, by the combination of different propor- 
tions of oxygen, with the same substance. The names 
by which these are distinguished, are given, for refer- 
ence, in the Appendix. 

334. Formation of Salts. — Most salts may be 
formed by simply bringing the proper acid and oxide 
together. Thus, as soon as liquid sulphuric acid and 
white magnesia come together, they unite and form 
sulphate of magnesia or Epsom salt. But the stimulus 
of heat is often required, particularly when the acid, 
as well as the oxide, is a solid substance. The affin- 
ity between acids and bases, is in accordance with 
the general law, that chemical attraction between 
substances is strongest in proportion as they are 
most unlike, or opposed to each other, in their proper- 
ties. 



332. What compounds do chlorine, iodine, sulphur, etc., form? 333. 
How are acids formed ? Give an example. 334. How are salts formed? 
Give an example. 



160 PRINCIPLES OF CHEMISTRY. 

335. Properties of Acids and Bases. — The proper- 
ties of these two classes of compounds are opposite, and 
when brought together, they neutralize each other. 
Thus, when acid and soda are brought together, the 
acid taste of the former and the alkaline taste of the lat- 
ter both disappear. Acids change certain vegetable 
blues to red. Bases restore the color. The experiment 
may be made with an infusion of litmus* in w r ater. 
A leaf of purple cabbage answers the same purpose. 
Acids color it red, while potash and the alkalies change 
the red to green. 

336. Effect of Heat to produce Combination. — 
It is seen from the foregoing, that heat is often essen- 
tial to chemical combination. This is almost always 
the case where both substances are solid. Beside 
heightening their chemical affinity, heat has the effect 
of destroying the cohesion, and of bringing the 
particles into closer and more general contact, and, 
within the range of affinity, by the melting or fusion 
which it accomplishes. Sulphur and iron, for ex- 
ample, require the aid of heat to bring about their 
union. The sulphur melts, and then combines with 
the iron. 

337. Further heating, has often just the contrary 



335. What are the properties of acids and bases ? 336. What is the 
effect of heat on chemical combination ? 337. Mention another effect of 
heat. 



• Litmus is a blue vegetable pigment much used by chemists for the purpose men- 
tioned in the text. 



LAWS OF COMBINATION. 161 

effect. It causes substances already combined, to sep- 
arate from each other again. This is especially the 
case when one of them is a gas. Thus, if oxide of silver 
or gold is heated, the oxygen passes off in the gaseous 
form and leaves the metal behind. 

838. Heat owes its decomposing effect, in this and 
similar cases, to the tendency which it imparts to cer- 
tain substances, to assume the gaseous form. And as 
all bodies would, probably, be gaseous, at a sufficiently 
high temperature, sufficient heat would probably de- 
compose all chemical compounds. 

339. Effect of Solution. — The solution of one or 
both of two substances to be combined, has, in a multi- 
tude of cases, the same effect, in promoting chemical 
combination, as that produced by heat. The reason is 
also the same. It destroys the cohesion of the particles, 
makes them movable, and brings them into more 
general and thorough contact. This is illustrated in 
the case of ordinary soda powders, the two constituents 
of which will not act on each other, unless one, at 
least, is dissolved. 

340. Electrical Relations of Elements. — The 
metals are sometimes spoken of as electro-positive and 
the metalloids as electro-negative, for reasons given in 
the chapter on Electricity. Electricity also resolves salts 
into the bases and acids which compose them. The 
acid goes to the positive pole, and is, therefore, electro- 



338. Why does heat have this effect ? 339. What is the effect of solu- 
tion ? 340. What are the electrical relations of the elements ? . 



162 PRINCIPLES OF CHEMISTRY. 

negative. The base goes to the negative pole, and is 
therefore, electro-positive.* 



* The laws of combination, and other subjects which belong to chemical philoso- 
phy, are further considered in the chapter on Salts, in the introduction to Organic 
Chemistry, and in the Appendix. Additional remarks on the atomic theory adopted 
In the text are also given in the Appendix. 



PART III. 

INORGANIC CHEMISTRY. 



CHAPTER I. 

NON-METALLIC ELEMENTS. 

341. Classification of Elementary Bodies. — The 
simple division of elementary bodies is into metals and 
non-metallic elements. The non-metallic elements 
are: — 

1. Oxygen, 5. Fluorine, 9. Arsenic,* 

2. Chlorine, 6. Sulphur, 10. Carbon, 

3. Iodine, t l. Nitrogen, 11. Silicon, 

4. Bromine, 8. Phosphorus, 12. Boron, 

13. Hydrogen. 



Oxygen. 

' Symbol 0; Equivalent, 8; Specific- Gravity, 1.1. 

342, Description. — Oxygen is a transparent and 
colorless gas, a little heavier than the atmosphere. It is 

341. How are elementary bodies divided ? 342. "What is oxygen ? 
Where does it exist ? 



* Arsenic is commonly regarded as a metal, but for reasons that will be given 
hereafter it is placed among the non-metallic elements. 



164 



PRINCIPLES OF CHEMISTRY. 



by far the most abundant substance in nature. About 
one-fourth, the weight of the air, eight-ninths of the 
waters of the globe, and probably half of the solid 
earth is oxygen. Oxygen is essential to the support of 
all forms of animal and vegetable life, and of ordinary 
combustion. 

343. Preparation of Oxygen. — Oxygen gas is ex- 
pelled from many substances which contain it by the 
simple agency of heat. Chlorate of potassa and black 
oxide of manganese are such substances. 

Mix equal quan- 
tities of chlorate of 
potassa and black 
oxide of mangan- 
ese and put one 
or two ounces of 
the mixture into a 
flask of green glass, 
(the flasks in which 
sweet oil is import- 
ed from Florence 
are well suited to 
this purpose,) adapt a cork to the mouth of the flask 
and insert through the cork a tube of sufficient length 
to reach the pneumatic cistern* when the flask is placed 
over a lamp as shown in figure 87. A jar is to be 
filled with water and inverted in the cistern to receive 

343. How is oxygen prepared ? Give the complete process. 




* A tub with a shelf across the center near the top forms a good pneumatic cistern. 



OXYGEJST. 



165 



the gas. After lighting the lamp the first portion of 
gas which comes over being mixed with the air pre- 
viously contained in the flask is to be allowed to escape, 
afterwards an abundance of gas may be collected in 
the manner shown in the figure. Each ounce of the 
mixed powder in the flask will give off about a gallon 
of oxygen gas. All other gases that are not absorbed 
by water may be collected in the same manner. 

Where a small quantity of oxygen only is required 
it may be collected by the simple apparatus shown in 
figure 88. Half a tea- 
spoonful of the dry mixed 
powder of chlorate of 
potassa and black oxide 
of manganese may be 
heated in a test tube con- 
nected air-tight with two 
clay pipes, as represented 
in the figure. The con- 
nections are made by winding the pipe-stems with strips 
of wet paper, folded in such a manner that the stopper 
thus formed tapers slightly toward the end. The first 
portions of gas, which contain an admixture of the air 
of the tube, are allowed to bubble through the water 
and escape. The rest is made to rise into a half-pint 
vial, which it gradually fills, by displacing the water. 
The vial has been previously filled with water, then 
covered with a bit of glass, and inverted in the water. 
If it is desired to hang it on the side of the bowl, a 
hook is then introduced, made of strong, doubled wire, 




166 PRINCIPLES OF CHEMISTRY. 

the two parts being kept about half an inch apart, and 
the vial is then hung, by its help, on the side of the 
bowl ; or this may be dispensed with, and the 
vial held by the hand in its proper place, while 
the gas is collected. When the process is com- 
pleted, vial and hook, if the latter has been used, 
are to be lowered into the bowl, the mouth being 
carefully kept below the surface ; the hook is then re- 
moved, the mouth covered with a bit of glass, and the 
vial then inverted upon a plate containing a little 
water, and so kept until it is wanted for an experiment. 
344. Explanation. — Black oxide of manganese may 
be employed alone as a source of oxygen but it does 
not yield this gas at the temperature employed in the 
above experiment. At a red heat part of the double 
portion of oxygen which the black oxide contains is 
expelled in a gaseous form. The mixture of this oxide 
facilitates the evolution of oxygen from the chlorate 
but the reasons are not well understood, for any other 

infusible powder answers 
the same purpose. 

345. A Simpler Meth- 
od. — The above methods 
of preparing oxygen are 
here given, because they 
illustrate the mode of 
collecting gases in large 
quantities, and make its accumulation visible to the 

344. Explain the process of making oxygen. 345. Give a simpler 
method of preparing oxygen. 







OXYGEN. 167 

eye. Tb* oxygen needed for the following experi- 
ments may be more conveniently prepared by placing 
the month of the test tube, containing the proper ma- 
terials, in a wide-mouthed vial, and heating, as before. 
As the gas is evolved, it will expel the air, and soon fill 
the vial. 

346. Iron Burned in Oxygen. — Make a coil of 
very fine iron wire, by winding the latter around a 
pencil ; fasten one end into the middle of a cork, by 
slitting the latter, and attach a fine splinter 
to the other end. Light the splinter, and 
introduce it into a vial of oxygen. The wire 
itself will take fire, and burn with brilliant 
scintillations. In this and the following ex- 
periments, the cork is to be placed loosely 
over the mouth of the vial, to prevent its 
violent expulsion by the heated gas. 

347. Explanation. — In this experiment the oxygen 
in the vial unites with the iron of the wire, and be- 
comes solid, in the form of oxide of iron. The oxide 
fuses into a small globule on the end of the wire, and 
occasionally falls, and melts its way into the glass. 
This is apt to be the case, even when water is left in 
the bottom, so that a vial is likely to be destroyed by 
this experiment. The process is exactly the reverse of 
that which takes place when binoxide of manganese is 
heated, to produce oxygen. In the one case, oxygen 



846, Bw can iron be burned in oxygen ? 347. What takes place in the 
above experiment ? 




168 PRINCIPLES OF CHEMISTRY. 

was driven from the metal ; in the other, it is drawn to 
it, though not in the same proportion. 

348. Taper Rekindled in Oxygen. — Introduce a 
newly extinguished taper or shaving, with a little fire 
at the end, into a vial of oxygen. It will be immedi- 
ately rekindled. This experiment may be many times 
repeated without a new supply of gas. 

349. Combustion is more vivid in pure oxygen, than 
in air, because the latter is diluted with other gases 
which do not take part in the combustion. 

350. Combustion of Phosphorus. — Place a piece of 
phosphorus, of the size of a pea, on a piece 
of chalk, slightly hollowed out for the pur- 
pose and connected with a cork by a fine 
wire. Ignite the phosphorus and introduce 
it immediately into a bottle of oxygen. It 
will burn with the utmost brilliancy, produc- 
ing a light which the eye can scarcely bear. 

351. The white fumes which fill the bottle in this 
experiment, are composed of particles of phosphoric 
acid, which are produced by the union of the phospho- 
rus and oxygen. They collect on the sides of the vial, 
and soon dissolve in water, which they absorb from the 
air. The water will be found to possess a sour taste, 
and to redden blue litmus paper, which is a character- 
istic of acids. 

352. Combustion of Charcoal. — Attach a small 



348. Describe the taper experiment. 349. Explain the last experiment. 
350. Describe the experiment with phosphorus. 351. What acid results 
from this experiment ? 352. Describe the experiment with charcoal. 





OXYGEN. 169 

piece of charcoal to a fine wire, ignite one end of it 
thoroughly, and introduce it into a vial of 93 

oxygen, haying a cork at the other end, as 
before. It burns with brilliant sparks. A 
piece of charcoal bark is best adapted to this 
purpose. 

353. Carbonic acid is formed in the above 
experiment, from the union of carbon with oxygen. It 
is a gaseous acid, and cannot be seen. Neither can it 
be detected by its taste. But a piece of moistened 
litmus paper, held for some time in the bottle, will be 
reddened by it, and proof of the presence of an acid 
may be thus obtained. "When wood burns it also 
yields carbonic acid. 

354. Definition of Combustion. — All of the above 
experiments are cases of combustion, and combustion 
may be defined as combination of any two substances, 
attended by light and heat. Metals which will not 
burn in the air, because it is diluted oxygen, burn 
brilliantly, as has been seen, in pure oxygen. 

355. Previous Heat required. — In order that most 
substances may burn, they must first be heated, to in- 
crease their affinity for oxygen. Take carbon, as an 
example. Before heating, its affinity for oxygen is not 
sufficient to bring about the requisite combustion. In 
this condition it may, therefore, lie for any length of 
time, in the air, or oxygen gas, without uniting with it. 
But heat stimulates the tendency to combination, and 

353. What is produced in this experiment ? 354. Define combustion. 
355. Why is heat required to start combustion ? 



170 PRINCIPLES OF CHEMISTRY. 

the bit of charcoal previously ignited, goes on burn- 
ing until it is consumed. The first particles ob- 
tain the necessary stimulus of heat, from the previous 
ignition, the next from the burning of the first, and 
so on. 

356. Uncombined Oxygen requisite. — Mere pres- 
ence of oxygen is not sufficient for combustion. It 
must be free, or uncombined oxygen. After burning 
charcoal in oxygen gas, the vial contains just as much 
oxygen as before, but being already combined, it has 
no affinity, or appetite, for more carbon, and therefore 
will not produce a new combustion. 

357. Each Particle in turn must be heated. — If 
the first particles that combine, do not communicate 
sufficient heat to the next, then the combustion stops. 
This may be illustrated by lighting a tightly wound 
roll of paper, and holding the flame upward. It is soon 
extinguished, because the heat that is produced by the 
combustion of one portion of the paper, is not communi- 
cated to the next, but passes off into the air. But if 
the taper be held with the flame downward, each par- 
ticle in turn receives the stimulus of heat necessary to 
combination, and the whole is consumed. 

358. Decay of Leaves and Wood. — The decay of 
leaves and wood is a sort of slow combustion, but not 
sufficiently vigorous to produce light and heat. In this 
case, as in the ordinary combustion of wood or coal, the 






356. What kind of oxygen is required for combustion ? 357. If each 
particle is not heated, what takes place ? Why ? 358. What causes the 
decay of wood ? 



OXYGEN. 171 

particles which have combined with oxygen pass off 
into the air, in an invisible form. 

359. Bleaching. — Bleaching may also be regarded as 
a kind of slow combustion. On exposing cloth to sun 
and air, its coloring matter is gradually burned up by 
the atmospheric oxygen. 

380. Oxygen a Purveyor for Plants.— It has 
been seen that both in combustion and decay, the oxy- 
gen of the air combines with the particles of leaves, 
wood and coal, and passes off with them in an invisible 
form. It flies off with them into the air, and yields 
them again to living plants, to produce new leaves, 
flowers and fruits. Indeed, they are entirely depen- 
dent, for their support, on what they thus obtain from 
the death and decay of their predecessors, through the 
agency of this ever active purveyor, the oxygen of the 
air. But for the fact that the particles of vegetable 
and animal matter can thus be used again and again, 
the supply would soon be exhausted, and vegetation 
cease upon the face of the earth. 

361. Relations to Life. — Oxygen is as essential to 
life, as it is to combustion. The diluted oxygen of the 
air, is better adapted to breathing, than pure air, but 
that which contains much less than its due proportion 
is no longer fitted to support life. Respiration consumes 
oxygen, so that the air of a close room is constantly 
being deprived of this essential constituent without ob- 
taining any new supply. As a consequence, it soon 

359. How may bleaching be regarded ? 360. Explain bow oxygen is a 
purveyor for plants. 361. What relation to life does oxygen sustain ? 



172 PRINCIPLES OF CHEMISTRY. 

becomes unfit to breathe. The case is similar to that 
of a taper burned in a bottle. The oxygen of the air 
in the bottle is gradually consumed, and the flame 
grows gradually more and more dim until it goes out. 
So life grows fainter and fainter, in a close unventi- 
lated room. 

Fish obtain oxygen from the air, rich in oxygen, 
which is dissolved in the water. See Section 539. 

362. Oxygen has been used, with great success, as a 
means of resuscitation, in cases of suffocation and drown- 
ing, when similar use of air was without effect. In 
such cases, it is forced into the lungs through a tube, 
from a jar or bladder. 

363. Ozone. — By passing an electrical current, con- 
tinually, through oxygen gas, for some time, it be- 
comes mysteriously changed in its properties. In this 
changed condition it is called ozone. It is, as it were, 
intensified in its affinities by the current, so that 
like chlorine, it will attack silver, and exhibit many 
other of the properties of the latter gas. The elec- 
tricity of the air has similar effects on the oxygen which 
it contains, and, in consequence of its varying electrical 
condition, the proportion of ozone is, also, from time to 
time, extremely varied. There is reason to believe 
that this substance has an important influence upon 
health, and that either its deficiency or excess is injuri- 
ous. In cholera seasons, it has been observed to be 
present in comparatively small quantity, while, during 

362. What is said of oxygen as a means of resuscitation ? 363. How is 
ozone produced ? 



CHLORINE. 173 

the prevalence of a species of influenza called " grippe," 
it is said to be more abundant. These observations 
need confirmation, by further experiments, before the 
facts can be regarded as fully established. The pres- 
ence of ozone, is indicated by the discoloration, 
through the influence of a current of air, of a test pa- 
per, prepared by moistening ordinary biblous paper 
with a solution of starch and iodide of potassium. This 
test paper becomes blue by the action of even a minute 
quantity of ozone. 

Chlorine. 

Symbol, CI; Equivalent, 35.5; Specific Gravity, 2.47. 

364. Description. — Chlorine is a yellowish green gas, 
of peculiar odor, about 2^ times as heavy as the air. 
More than one-half of common salt is chlorine. Salt 
mines and the ocean, therefore, contain it in immense 
quantities. 

365. Preparation of Chlorine. — Chlorine is pre- 
pared from muriatic acid, which is composed of chlo- 
rine and hydrogen, by using some agent to retain the 
latter and liberate the former. Black oxide of man- 
ganese is such a substance. 

The oxide of manganese is placed in a flask and 
covered with muriatic acid poured in through the fun- 
nel and safety-tube, F, figure 94, and a gentle heat is 

364. What is chlorine ? Where is it found ? 365. How is chlorine pre- 
pared? Describe the process. 



174 



PRINCIPLES OF CHEMISTRY. 




applied by the lamp, L. As the gas comes off it is 
passed through a bottle, B, containing a little water to 

absorb any 
muriatic 
acid that 
passes over 
in vapor, 
and the gas 
is collected 
over the 
pneumatic 
cistern, C, 
in a jar, J, 
filled with 

hot water, to prevent absorption of the gas, which is 
largely absorbed by cold water. A strong solution of 
common salt, may be used instead of hot water in col- 
lecting chlorine, as it does not absorb this gas even at 
the common temperature. 

366. Collection by Displacement. 
— As chlorine is heavier than air it 
may be collected by displacement by 
the simple apparatus shown in figure 
95. The oxide of manganese placed 
in a phial is well covered with muriatic 
acid and kept warm by a cup of hot 
Water, as represented in the figure. Chlorine gas soon 
displaces the air in the second vial. It should be corked 
as soon as filled. 




366. Give the process of collecting chlorine by displacement. 



CHLORINE, 



175 



96 



367. It will be remembered that black oxide of man- 
ganese, is a substance containing a large portion of 
oxygen, part of which is feebly held, and very willing 
to go. Its use in making chlorine depends on this fact. 
The loosely held oxygen, seizes upon the hydrogen of 
the muriatic acid, remaining with it as water, and at 
the same time setting its chlorine at liberty. 

368. A Simpler Method. — Acids expel chlorine 
from many bases which have previously been made to 
absorb it. Lime is one of these bases. Pour into a 
wide-mouthed, half-pint vial, a table-spoon- 
ful of dilute sulphuric acid, and add rather 
more than the same bulk of chloride of 
lime or bleaching powder. It is best to add 
it in small portions, covering the vial with 
a cork or bit of glass after each addition. 
The vial will soon be filled with faintly 
green chlorine gas. More of the materials will be re- 
quired, if the chloride of lime is deteriorated by ex- 
posure to the air, as is often the case. The 
gas thus produced, may be used for most 
of the experiments which follow, without 
transferring it to another vessel. 

369. Chloride Heavier than Air. — 
This is already imperfectly proved, in the 
first method of collecting chlorine, but the 
following proof is more satisfactory. The 
gas produced in the last experiment, may be slowly 





367. Explain the process. 368. Describe another method of preparing 
chlorine. 369. What proof that chlorine is heavier than air. 



176 PRINCIPLES OF CHEMISTRY. 

poured from the vessel containing it, into another wide- 
mouthed vial. The second vial, if the smaller of the 
two, may be thus filled without receiving any acid from 
the first. This experiment should be conducted in 
the open air or under a large flue as even a small 
quantity of chlorine produces considerable inconve- 
nience and irritation to the lungs of the operator. In 
small quantities the gas cannot be seen to flow, but will 
actually pass from one vessel into the other. Its pres- 
ence may be proved by the methods given in the fol- 
lowing experiments. 

370. Chlorine dissolves in Water. 
— Having filled a vial with chlorine, 
by the first of the methods above de- 
scribed, cork it, and open it under 
water, contained in a bowl. As the 
gas dissolves in the water, the latter 
will rise to take its place. "When it 
has risen a little way, cork and shake the vial, and open 
it again below the surface. The water will then rise 
and dissolve still more of this gas. The solution is to 
be set aside for a subsequent experiment. Gas pro- 
duced by the last method above described, may also be 
used in this experiment, if previously transferred to 
another vial. 

371. Action of Chlorine on Metals. — Chlorine 
gas combines with many metals, converting them into 
chlorides. Their action may be illustrated by sprink- 

370. What proof that chlorine dissolves in water ? 371. Describe the 
action of chlorine on metals. 




CHLORINE. 177 

ling finely pulverized antimony into a bottle of chlo- 
rine. Each particle of metal ignites as it falls through, 
the gas ? and a miniature shower of fire is thus produced. 
The white smoke which is produced in this experiment, 
is composed of minute particles of chloride of anti- 
mony. Potassium, tin and arsenic also take fire spon- 
taneously in this gas, and iron and copper in fine 
powder when moderately heated take fire in the same 
manner. Yapor of mercury admitted into a jar con- 
taining chlorine takes fire and burns with a brilliant 
flame. 

372. Nascent Chlorine. — Nascent chlorine, in its 
action on the metals, is the most powerful agent known. 
Even the noble metals yield to its power, and waste 
away in the liquid which contains it. The term nas- 
cent signifies being born, or in the act of formation, or 
escape from a previous combination. 

373. All gases are most energetic, in their action at 
the first moment of their separation from compounds 
which contain them, and while they may be regarded 
as still retaining the solid form themselves. The subse- 
quent expansion into the gaseous form, diminishes their 
energy. 

374. Nascent chlorine is best obtained by mixing 
hydrochloric acid with half its bulk of strong nitric 
acid. Such a mixture is called aqua regia. The lat- 
ter acid compels the former to yield a constant supply 



372. What is the action of nascent chlorine ? 373. What is the general 
fact in relation to nascent "bodies ? 374 How is nascent chlorine best 
obtained ? 

8* 




178 PRINCIPLES OF CHEMISTRY. 

of its own chlorine in the nascent condition. It does 
this, by means of its oxygen, which seizes upon the 
hydrogen of the hydrochloric acid, forming water, and 
setting its chlorine at liberty. The remnant of the 
nitric acid escapes, as in the case of its action on metals 
hereafter described. 

375. Chlorine decomposes "Water. — If chlorine 
water be exposed to the sun for some days, it loses its 

green color. The chlorine combines 
with the hydrogen of the water, form- 
ing hydrochloric acid, and sets its oxy- 
gen at liberty. If the experiment be 
made in a bottle, inverted in water, so 
that the oxygen may collect, bubbles of this gas will 
be found above the liquid. This experiment proves 
the powerful affinity of chlorine for hydrogen. 

376. Bleaching by Chlorine. — Introduce bits of 
printed muslin into the solution of chlorine before ob- 
tained. Most colors will soon disappear. If the solu- 
tion is weak, the bleaching effect will be better shown 
with infusion of litmus or red cabbage. Color may 
also be removed from cloth or paper by hanging the 
article to be bleached, previously moistened with water, 
in a vial of gaseous chlorine. 

377. Chlorine water may be prepared in larger quan- 
tity by leading the gas directly into water. The second 
of the two methods before described, will be found the 
most advantageous. 

375. Does chlorine decompose water ? 376. How is calico bleached by 
chlorine ? 377. How is chlorine water best prepared ? 



CHLORINE. 179 

378. Oxygen the real Bleaching Agent. — The 
real bleaching agent in this method of bleaching, is the 
same as that mentioned in paragraph 359. It is oxy- 
gen, always present during the process, as an element 
of the water which moistens the material. The chlor- 
ine simply acts to bring nascent oxygen into activity. 
It does this by depriving it of the hydrogen with which 
it is combined. The oxygen having thus lost its com- 
panion, looks about, as it were for something else with 
which to combine. The coloring matter of the cloth 
being the first thing at hand, is destroyed by the ex- 
treme energy of its affinity. 

379. Action of Nascent Oxygen. — The superior 
force of an element in its nascent condition is strik- 
ingly shown in the above experiment. A piece of 
printed muslin hung in a bottle of oxygen gas would 
not lose its color. But the nascent oxygen which 
chlorine liberates, begins to destroy the coloring matter 
on the first instant of its liberation. 

380. Chlorine and Turpentine. — Im- 
merse a rag wet with camphene or spirits 
of turpentine in a vial of chlorine gas. It 
is immediately inflamed, with the produc- 
tion of dense black smoke. Spirits of tur- 
pentine is composed of hydrogen and car- 
bon. The hydrogen combines so energeti- 
cally with chlorine, as to produce flame in the above 



378. Explain how chlorine bleaches. 379. Show the advantage of nas- 
cent oxygen. 380. Describe the inflaming of turpentine by chlorine. 




180 PRINCIPLES OF CHEMISTRY. 

experiment, while the carbon is separated in the form 
of black particles, which constitute the smoke. 

381. Use as a Disinfectant. — As chlorine destroys 
color, when used as a bleaching agent, so it destroys 
noxious vapors in the air. Its minute atoms fly forth 
like birds of prey, seizing on the impurities of the at- 
mosphere and devouring them. Chloride of lime is 
commonly substituted for chlorine for this use. A little 
of this salt is placed in a saucer and moistened, when it 
gradually yields chlorine through the action of the car- 
bonic acid of the air. Stronger acids evolve it abun- 
dantly. 

382. Chlorine a Destructive Agent. — Chlorine, 
as has been seen, is one of the most destructive of all 
substances. It not only destroys colors and odors, but 
any kind of vegetable or annual matter long submitted 
to its action, wastes away and is destroyed. It does 
this partly by its own direct action, and partly by let- 
ting loose the atoms of nascent oxygen, as before de- 
scribed. 

383. In what sense Destructive. — It is always to 
be borne in mind that the term destruction is used in 
chemistry in an entirely figurative sense. Thus, neither 
oxygen nor chlorine, strictly speaking, destroy. They 
only combine with the particles of the substances they 
seem to destroy, forming new, and often invisible com- 
pounds. Many of these wdll be hereafter mentioned. 



381. Is chlorine a disinfectant ? Why? 382. What is said of chlorine 
as a destructive agent ? 383. In what sense is it destructive ? 



IODINE. 181 

384. Relations to Animal Life. — Chlorine is a 
poisonous gas. No danger, however, is to be appre- 
hended from the escape of small portions into the air 
during the preceding experiments. The diluted gas, 
however, is apt to produce irritation of the throat and 
consequent coughing. 

385. Resemblance to Oxygen. — In many respects 
chlorine is similar to oxygen, as has already been 
shown. It combines with almost all of the elements, 
and with many compounds. This combination is often 
attended with light and heat, and is therefore combus- 
tion. The metal antimony, for example, as has already 
been shown, will burn in chlorine gas even without 
previous heating. 

386. Compounds of Chlorine and Oxygen. — Chlo- 
rine combines with five atoms of oxygen to form chlo- 
ric acid. This acid is of importance, principally, as a 
constituent of the chlorate of potassa, analogous in its 
leading properties to nitrate of potassa. Hypochlorous 
acid, a constituent of bleaching powders, is another 
compound of chlorine with oxygen. It is again men- 
tioned in the section on chlorides. 

Iodine. 

Symbol, I; Equivalent, 126; Specific Gravity of Vapor, 8.Y. 

387. Description. — Iodine is commonly seen in the 



384. Give the relations of chlorine to animal life. 3S5. In what re- 
spects does chlorine resemble oxygen ? 386. Mention some compounds 
of chlorine and oxv°:en. 387. What is iodine ? Where is it found ? 



182 



PRINCIPLES OF CHEMISTRY. 



form of brilliant blue-black scales, somewhat similar to 
plumbago in appearance. In odor it resembles chlo- 
rine. It is found in the water of the ocean, in sea- 
weeds, sponges, &c, but always in combination with 
sodium or some other metal. Minute traces of it are 
found to exist in the atmosphere, and thence are trans- 
ferred to the bodies of animals. 

S88. Preparation. — For the preparation of iodine, a 
101 lye made from the ashes 

of certain sea-weeds is 
heated with oil of vitriol 
and black oxide of manga- 
nese. The liberated oxy- 
gen of the latter expels 
HP^ vapors of iodine from the 
mixture. These being led into a receiver, crystallize in 
brilliant scales. A retort and receiver are commonly 
used in the process. The ashes of sea-weeds employed 
for the purpose are called ~kel/p, and are prepared in 
102 g rea t quantities on the coast of Scotland. 

389. Violet Vapors of Iodine. — Introduce 
a few scales of iodine into a test-tube or vial, 
and heat it for a moment over the spirit lamp, 
The solid iodine is immediately converted into 
a beautiful violet vapor, which fills the vial. 
As the latter cools, the iodine becomes again 
solid, in the form of minute crystals. On warm- 
ing these crystals the color re-appears. 




388. Explain the manufacture of iodine. 389. How are violent vapors 
of iodine produced ? 



IODIXE, 



183 



390. Coloring- Effect on Starch. — Heat a little 
iodine in a pipe bowl, and as soon as vapors appear, 
blow thein against a sheet of paper covered with figures 
made with thin starch paste. The iodine 103 
vapor immediately colors them bine. The 
paste may be made in a test-tube, over a 
spirit lamp. 

391. Application of the Test for Iodine. — Bum 
a common sponge and having carefully collected the 
ashes place them in a test-tube, A, with an equal bulk 
of black oxide of manganese and add a little oil of 

104 





vitroil ; close the mouth of the tube with a cork through 
which is passed a tube leading into a phial, B, contain- 
ing a solution of starch as shown in figure 104. On ap- 
plying a gentle heat the vapor of iodine will pass 
over and produce a beautiful blue color by union with 
the starch. 



390. Describe the effect produced by iodine on starch paste, 
an instance of the application of this test. 



391. Give 



184: PRINCIPLES OF CHEMISTRY. 

892. Engravings Copied by Iodine. — A transient 
copy of an engraving, or other printed matter, may be 
made, by exposing it to faint fumes of iodine, and then 
pressing it down upon paper moistened with vinegar, 
or dilute nitric acid. The vapors, adhere to the ink 
only, and are transferred by pressure ; producing, w T ith 
the starch contained in ordinary letter paper, a blue 
impression. 

393. Poisoning by Iodine. — Iodine is much used as 
a medicine, but it is sometimes swallowed by accident in 
too great quantity, and it then acts as a corrosive poison. 
The antidote for iodine is starch which forms with it 
a harmless compound. 

Bromine. 

Symbol, Br; Equivalent, 78; Sp. Gr, of Vapor, 5.34; Sp. Gr. of Liquid, 3.2. 

394. Bromine is a dense reddish-brown fluid, exhal- 
ing at ordinary temperatures a deep orange-colored 
vapor. It is similar, in its chemical properties, to 
chlorine, but the latter is the stronger of the two and 
expels bromine from its compounds. Thus, if chlorine 
be passed into one end of a heated tube containing 
bromide of silver, the vapors of bromine will be seen 
to pass out at the other end, and escape, while the chlo- 
rine remains, and takes possession of the metal. Bro- 
mine, like chlorine, is found in sea-water and in the 



392. How are engravings copied by iodine ? 393. What is the proper 
antidote for poisoning by iodine ? 394. What is said of bromine ? 



FLOUEOE. 185 

water of mineral springs, combined with sodium or 
some other metal. Bromine has also been found in 
an ore of silver from Mexico, in which bromide of silver 
is found mixed. with chloride of silver. The power of 
chlorine to expel it from its compounds is made use of 
in manufacturing bromine. This substance is used in 
photography, but is otherwise of little general interest. 
Although widely distributed, it exists in nature in com- 
paratively small quantities. Bromine vapors have the 
effect of imparting to starch a beautiful orange color. 
Bromine is freely dissolved by both alcohol and ether, 
and like iodine it acts as a corrosive poison, for which 
starch is the best domestic antidote. 



Fluorine. 

Symbol, F; Equivalent, 19; Specific Gravity, 1.3. (?) 

395. Fluorine is a yellow-brown gas, of strong odor, 
somewhat similar to that of chlorine. It is one of the 
elements of the beautiful mineral fluor spar. It is 
prepared from the fluoride of potassium, by means of 
the galvanic current. Its isolation has been attended 
with great difficulties, and the gas is therefore imper- 
fectly known. Its principal compounds are hydrofluoric 
acid and fluor spar, to be hereafter described.* 

395. What is said of fluorine ? 



* Many compounds of chlorine, bromine, iodine and fluorine, with each other and 
with oxygen, are known to the chemist, but they are without interest to the general 
student. 



186 PRINCIPLES OF CHEMISTRY. 

Sulphur. 

Symbol, S; Equivalent, 16; Specific gravity, 2.05. 

396. Description. — Sulphur is a brittle yellow solid, 
twice as heavy as water, burning with a peculiar odor 
made familiar in the ignition of common friction 
matches. With the metals it forms sulphides or sul- 
phurets. In Sicily and certain other volcanic regions, 
it occurs in beautiful, yellow crystals. Gypsum, and 
iron pyrites or fools' gold, represent the two principal 
classes of minerals that contain it. It also enters in 
small proportion into the composition of all animal and 
vegetable substance. It is the sulphur in eggs that 
blackens the silver spoon with which they are eaten. 
Sulphur is insoluble in water and consequently taste- 
less. 

397. Preparation. — In preparing commercial sul- 
phur, the impure material of volcanic regions is highly 
heated, and thus made to fly off as vapor, leaving its 
earthy impurities behind. The vapors are condensed 
as flowers of sulphur. The process by which a solid is 
thus vaporized, and re-converted into a solid, is called 
sublimation. Native sulphur may also be partially 
purified by simple fusion. Its earthy impurities hav- 
ing settled, it is poured off into molds and thus con- 
verted into roll brimstone. 



396. What is sulphur ? Where does it occur ? 397. Describe the manu- 
facture of sulphur? 




SULPHUR. 187 

398. Sublimation of Sulphur. — The subli- 105 
mation of sulphur may be shown by heating 
a small bit of the substance in a test-tube. 
Flowers of sulphur will deposit in the upper 
portion of the tube. 

399. Combustion of Sulphur. — Melt some 
flowers of sulphur upon the end of a wire 
wound with cotton thread, and hang them after 
ignition in a vial of oxygen gas. The oxygen 
gas combines with the sulphur, forming a new compound 
gas, called sulphurous acid. A brilliant blue 106 
flame accompanies the combination. It thus 
appears that acids may be gaseous as well as J|§? 
liquid. The acidity may be proved, as usual, ifer W 
by blue litmus paper. §R-i rjm 

400. Bleaching by Sulphur. — Introduce j 

a red rose or other flower into a vial filled ! s 

with sulphurous acid. It will soon lose its color. 
Wash it with dilute sulphuric acid and the color re- 
appears. This experiment may also be made in a 
bottle in which sulphur has been burned in common 
air. 

401. Explanation. — Sulphurous acid forms a white 
compound with the red coloring matter of the rose. It 
may seem incomprehensible that a colorless gas and 
red coloring matter should unite to form white, and it 



898. How may the sublimation of sulphur be shown ? 399. What is 
said of the combustion of sulphur? 400. Describe the process of 
bleaching by means of sulphur. 401. Why does sulphurous acid 
bleach? 



188 PRINCIPLES OF CIIEMISTRY. 

would be so, were the case one of mere mixture. But 
it is an instance of chemical combination, in which, as 
is often the case, the properties of the constituents en- 
tirely disappear. When sulphuric acid is afterward 
used, the color re-appears, because the stronger acid 
has expelled the weaker, and has itself no inclina- 
tion to form with the coloring matter a similar com- 
bination. 

402. Straw Bleaching. — The bleaching of straw 
goods is always effected by sulphurous acid. They are 
first moistened, and then exposed to the fumes of burn- 
ing sulphur. An inverted barrel is often made to serve 
the purpose of a bleaching chamber. Articles thus 
bleached by sulphurous acid, after a time, regain their 
color. This is not the case in chlorine bleaching, be- 
cause the coloring matter is not merely changed, but 
destroyed. This agent is not applicable to straw, on 
account of a faint brown tinge which it imparts to the 
material. 

403. Copying Medallions. — Sulphur melts, readily, 
by application of heat. (239° F.) At a higher tem- 
perature it thickens again. (350° F.) Still further 
heating makes it again fluid (at 500°. F.) In this 
second period of fluidity, it has the remarkable property 
of assuming a waxy consistence on being poured into 
water. In this condition it is used for copying seals, 
coins, and medals. The copy acquires, in a few hours, 



402. Describe the process of straw bleaching. 403. Explain the copy- 
ing of medallions by sulphur. 





SULPHUROUS ACID. 189 

the original hardness of sulphur. The 
plastic material may be obtained in the 
form of elastic strings, by pouring mol- 
ten sulphur from a test-tube into cold 
water. 

404. Sulphur Crystals. — Sulphur 
may be obtained in a crystalline form, 
by melting it in a pipe bowl, at a gentle heat, and 
then allowing it to cool. A crust soon forms 108 
on the top, which is broken, and a portion of 
the liquid sulphur below poured out. On 
breaking the pipe, it is found filled with crystals, 
shooting across the interior from the incrusted walls. 

Sulphurous Acid. S0 2 . 

405. Description. — Sulphurous acid is a gas, having 
the smell of a burning match. It is composed of sul- 
phur and oxygen, in the proportion of one atom of the 
former to two of the latter. The termination " ous" 
indicates, as in other cases, a smaller proportion of oxy- 
gen than is contained in some other acid composed of 
the same elements. 

406. Preparation. — It has already been shown that 
this acid may be prepared by burning sulphur in oxy- 
gen. A better method is to heat in an earthen retort, 
or in a flask made of hard glass, two parts of flowers 
of sulphur intimately mixed with three parts of black 

404. How may crystals of sulphur be obtained? 405. What is sulphu- 
rous acid ? 406. How is sulphurous acid prepared ? 



190 



PRINCIPLES OF CHEMISTRY. 



109 



oxide of manganese in fine powder. The gas having 
been passed through a bottle of water to remove a lit- 
tle vapor of sulphur and sulphuric acid which is carried 
over may be collected in another bottle of water, 
forming a strong solution of sulphurous acid, or the 
gas may be collected in a dry bottle for examination. 
Sulphurous acid may also be obtained in the liquid form 

free from water 
by means of 
the apparatus 
shown in the 
figure. The ma- 
terials for pre- 
paring the gas- 
eous acid are 
placed in the 
flask, A, heated 
by a lamp. The 
gas is puri- 
fied by passing 
through con- 
centrated sul- 
phuric acid in 
the bottle, B, 
and then trans- 
mitted through the pewter worm, C, surrounded by a 
freezing mixture of ice and salt, and collected in the 
receiver, D, which is also kept in a freezing mixture. 
From the bottle, D, it may be transferred to tubes and 
hermeticallv sealed and kept for future use. At ordi- 




SULPHUROUS ACID. 



191 



nary temperatures this acid would again assume the 
gaseous form, and at 60° F. it exerts a pressure of two 
and a half atmospheres. 

407. A Simpler Method of preparing this gas for 
experiment is to heat oil of vitriol with bits of copper. 
The oil of vitriol is thus deprived of part of its oxygen, 
and converted into sulphurous acid. The process may 
be conducted in a test-tube. 
By leading the gas through a 
smaller tube into a vial partly 
filled with water, a solution of 
sulphurous acid may be ob- 
tained, possessed of the same 
bleaching and other properties 
as the gas itself. "When the 
evolution of the gas commences, the heat of the lamp 
is no longer required. 

408. Explanation. — Copper has a very strong affinity 
for oxygen, and takes it from the oil of vitriol, which 
possesses it in large proportion. The oil of vitriol, 
thus deprived of part of its oxygen, is converted into 
sulphurous acid gas. 

409. Use in preserving "Wines. — Sulphurous acid, 
in small quantities, is sometimes added to wine to pre- 
vent its souring. This change is owing to the absorp- 
tion of oxygen from the air. Sulphurous acid is a sub- 
stance possessed of an excessive appetite or affinity for 




407. By what other method may this gas be prepared ? 408. Explain 
the process. 409. Why is sulphurous acid sometimes added to wine? 



192 PRINCIPLES OF CHEMISTRY. 

oxygen. A small portion of it in a wine cask will 
seize on what little oxygen finds admission, and so pre- 
vent the deterioration of the wine. It destroys itself 
in this act of protection, and is converted into sulphu- 
ric acid. Sulphurous acid in the form of sulphite of 
lime is also used to stop the fermentation of cider when 
it has acquired a pleasant flavor ; for this purpose one 
ounce of the sulphite is added to every gallon of cider. 

410. Use in Sugar Manufacturing. — The oxygen 
of the air so modifies the juice of the sugar-cane, that 
it cannot be made to yield its due proportion of sugar. 
Sulphurous acid, by appropriating the oxygen to itself, 
prevents this effect, and is said to double the product. 
It is generally used in the form of its lime compound, 
called sulphite of lime. The objection to its use con- 
sists in the slight sulphurous taste which it imparts to 
the sugar. But this is said to be removed by clarifica- 
tion, at a loss of ten per cent., leaving still a large gain 
from the employment of the process. The bleaching 
effects of sulphurous acid have already been illustrated. 

411. Disinfecting Properties. — Sulphurous acid is a 
powerful disinfectant. The fumes of burning sulphur 
by preventing oxidation check the first development of 
animal and vegetable life. In the same manner it pre- 
vents putrefactive fermentation and decomposition, and 
immediately destroys all animal odors and emanations. 
For these purposes it is in many respects preferable to 
chlorine. The fumes of burning sulphur are employed 

410. How is sulphurous acid employed in manufacturing sugar ? 411. 
For what other purpose is sulphurous acid employed ? 



SULPHURIC ACID. 193 

to cleanse apartments that have been occupied by 
patients with contagious diseases. 

Sulphuric Acid. SO 3 = 40. 

Oil of Vitrol; HO J S0 3 = 49. 

412. Description. — Sulphuric acid is a colorless, oily 
fluid, of intensely acid taste, known in commerce as oil 
of vitriol. It is composed of sulphur and oxygen, in 
the proportion of one atom of the former to three of 
the latter. It also contains water, with which it is 
chemically combined. As it is among the most impor- 
tant of all chemical products, the process of its manu- 
facture will be given with some detail. 

413. Preparation. — Sulphuric acid may be made 
directly from its elements, by igniting a mixture of air 
and vapor of sulphur with a red-hot iron. Sulphuric 
acid was formerly prepared by distilling sulphate of 
iron called copperas, or green vitriol, and hence the oily 
acid thus obtained was called oil of vitriol. In quan- 
tity, it is now generally made from sulphurous acid, by 
imparting to the latter additional oxygen. Take a bot- 
tle in which sulphur has been burned, and which there- 
fore, contains sulphurous acid, and hold in it, for a short 
time, a rod or stick moistened with nitric acid. The 
gaseous sulphurous acid obtains oxygen from the nitric 
acid, which is rich in this element^ and very liberal of 
it, and thereby becomes sulphuric acid. A little water, 

> 412, Describe sulphuric acid. 413. How many sulphuric acid be pre- 
pared ? 




194 PRINCIPLES OF CHEMISTRY. 

previously placed in the bottom of the vial, absorbs 
the acid thus formed. To acidify the water 
to any considerable extent, it will be neces- 
sary to burn sulphur, and introduce the 
moistened rod repeatedly. That the acid is 
not the sulphurous or the nitric acid, em- 
ployed in the process, may be proved by 
using it with zinc to make hydrogen gas. 
414. Remark. — The red fumes which fill 
the vial in the last experiment, consist of the changed 
nitric acid, (nitric oxide,) which has just given up part 
of its oxygen, and is now resuming part of it from the 
air. It thereby becomes a third substance, of a red 
color, to be again mentioned in the section on nitric 
acid. 

415. Manufacture of Oil of Yitriol. — The method 
of the production of oil of vitriol on a large scale, is 
essentially the same as that above given. Fumes of 
burning sulphur and vapor of nitric acid, with air and 
steam, are introduced into a leaden chamber, when the 
process proceeds, as before described. 

416. Comparatively little nitric acid is needed in the 
process, for it is found that while it yields oxygen to the 
sulphurous fumes, the changed acid greedily seizes oxy- 
gen from the air of the chamber, and imparts it again, 
to keep up the process. The air is, therefore, the real 



414. What causes the red fumes in the above experiment ? 415. Ex- 
plain how sulphuric acid is manufactured. 416. Why is but little nitric 
acid required ? 




SULPHURIC ACID. 195 

oxidizer, while the changed nitric acid only acts to 
transfer it to the sulphurous fumes. 

417. Description of Acid Chambers. — The figure 
represents one 
form of the 
leaden cham- 
bers employed 
in the above 
manufacture. Connected with them are a steam 
boiler and two furnaces, in one of which sulphur 
is burned, and converted into sulphurous acid. Over 
the sulphur is another vessel, containing the mate- 
rials for making nitric acid, the formation of which 
commences as soon as the sulphur flame has imparted 
the requisite heat. The vapors thus produced, are 
mingled with air and steam in the leaden chamber. 
How they act together to produce sulphuric acid, has 
been already explained. The space is divided by a 
partition, in order that all the materials may be more 
thoroughly mixed, as they pass through the narrow 
opening below it. The acid, as it forms, dissolves in 
water which covers the bottom of the chamber, and is 
thus collected. Lead is used as a lining for the cham- 
bers, because the acid would destroy almost any other 
material that might be employed. 

418. The dilute acid obtained from the chambers, is 
concentrated first in leaden vessels, and afterward, 
when it has become strong enough to corrode the lead, 

417. Describe the acid chambers. 418. How is the acid chamber con- 
structed ? 



196 



PRINCIPLES OF CHEMISTRY. 



in retorts of platinum. The metal platinum being of 
about half the value of gold, the vessels in which the 
evaporation is carried on are extremely expensive. 
Some manufactories deliver tens of thousands of pounds 
of sulphuric acid per day. 

This method of manufacturing sulphuric acid is 
called the English process, because it was first practiced 
in England. 

419. Illustration. — This process of manufacturing 
sulphuric acid may be illustrated in the lecture-room 
by means of the apparatus shown in the figure. A large 
receiver, A, is filled with air and communicates with 

113. 




the atmosphere by the tube a. The flask, B, contains a 
mixture of sulphur and black oxide of manganese from 
which sulphurous acid is produced by the heat of a small 
furnace ; binoxide of nitrogen is supplied by the jar, C, 

419. How may the manufacture of sulphuric acid be illustrated ? 



SULPHURIC ACID. 197 

by the action of nitric acid upon fragments of copper ; 
copious red fumes of peroxide of nitrogen are formed 
by the union of the air in the balloon, A, with the bin- 
oxide of nitrogen. In a few minutes the inside of the 
balloon becomes coated with a white crystalline de- 
posit formed by the union of sulphurous acid, peroxide 
of nitrogen and water. Steam is then supplied by the 
tube, S, when the crystalline deposit is immediately dis- 
solved and decomposed with brisk effervesence ; bincx- 
ide of nitrogen escapes, and sulphuric acid remains in 
solution. The binoxide of nitrogen again absorbs air 
and reappears in red fumes as peroxide of nitrogen, 
which again unites with sulphurous acid and water to 
form white crystals, which are, in their turn, dissolved 
and decomposed as before, forming a fresh portion of 
sulphuric acid. In this manner a small quantity of bin- 
oxide of nitrogen acts repeatedly as a carrier of oxygen 
from the air to the sulphurous acid, converting it into 
sulphuric acid. In the large chambers where sulphuric 
acid is manufactured on a large scale, all these changes 
go on simultaneously. 

420. Comparative Strength of Sulphuric Acid. — 
Sulphuric acid is the strongest of all acids. This may 
be shown by bringing it to a direct trial of strength with 
other strong acids. If poured, for example, on nitrate 
of potassa, which is, as its name applies, a compound 
of nitric acid and potassa, it takes sole possession of the 
base, and expels the nitric acid in the form of vapor. 

420. How is the strength of sulphuric acid shown ? 



198 PRINCIPLES OF CHEMISTRY. 

It expels muriatic acid from its compounds in the same 
manner. This is the method by which nitric and mu- 
riatic acids are always obtained. Whatever they can 
accomplish when free, may therefore be traced back to 
the power of sulphuric acid which gave them their 
liberty. The latter is the king among the acids, who 
accomplishes indirectly what he cannot effect in per- 
son. The solution of the noble metals by aqua regia is 
one among these indirect results. 

421. Sulphuric acid is volatile at high temperatures. 
Phosphoric and other non- volatile acids, are, therefore, 
under certain circumstances, superior to it. This is 
illustrated in certain crucible operations, where com- 
pounds containing sulphuric acid are heated with such 
acids. The sulphuric acid is then easily dispossessed, 
and compelled to take refuge in flight. 

422. Action of Sulphuric Acid on Metals. — Sul- 
phuric acid attacks all metals with the exception of 
platinum and gold. Even the dilute acid acts on all 
the metals hereafter named, as far as manganese. 

The action of the dilute acid may be illustrated by 
placing a few bits of zinc in a tumbler, with a little 
water, and adding a small portion of oil of vitriol. 
The metal dissolves with the evolution of hydrogen 
gas. The reason of the evolution of this gas is given in 
the section on hydrogen. 

The action of the strong acid may be illustrated, by 

421. 19 it strongest at high temperatures ? 422. What is the action of 
sulphuric acid on metals ? Illustrate the action oi the dilute acid. Il- 
lustrate the action of the strong acid ? 



SULPHURIC ACID. 199 

heating a little copper, with oil of vitriol, in a test-tube. 
The metal dissolves with the evolution of sulphurous 
acid fumes. The reason of the appearance of sulphu- 
rous acid is given in Section 408. 

423. Affinity for "Water. — The affinity of sul- 
phuric acid for water is so strong that it lavs hold on 
every particle of the invisible aqueous vapor of the at- 
mosphere. It finds it in what seems the driest air ; 
and every particle which it catches it retains. It grows 
in bulk by what it thus drinks, as will be seen if a lit- 
tle oil of vitriol is left exposed to the air, for a few 
days, in an open vessel. It is sometimes necessary, in 
chemical operations, to free gases from all the aqueous 
vapor which is mixed with them. This is done com- 
pletely by causing them to bubble through oil of vitriol, 
and again collecting them. 

424. Heat by Dilution. — "When sulphuric acid and 
water are mixed, condensation takes place, accompanied 
by elevation of temperature. Fifty cubic inches of 
sulphuric acid and fifty cubic inches of water, when 
mixed, do not fill a vessel of the capacity of one hun- 
dred cubic inches, but fall about three inches short. 
Condensation has therefore taken place to the amount 
of three inches. Heat is, as it were, pressed out in 
such cases, as explained in the early part of this 
work. 

425. "Wood Charred by Sulphuric Acid. — Wood 



423. What is said of the affinity of sulphuric acid for water ? 424. 
WTiat takes place when sulphuric acid is diluted ? 425. Why does sul- 
phuric acid char wood ? 



200 PRINCIPLES OF CHEMISTRY. 

dipped in oil of vitriol is soon charred. Wood is com- 
posed of carbon, hydrogen and oxygen. The last two 
together form water. The affinity of sulphuric acid 
for water has been mentioned above. The acid and 
the wood being in contact, it would seem that the hy- 
drogen and the oxygen of the latter agree to combine 
and satisfy this demand. The carbon being at the 
same time isolated, appears in its natural black color. 
Sulphuric acid exerts a similar action on other vegeta- 
ble substances. 

426. Important Uses of Sulphuric Acid. — Sulphu- 
ric acid is largely employed for dissolving indigo, for 
use in dyeing and calico printing ; also, for converting 
common salt into sulphate of soda, as a preparatory 
step to the manufacture of carbonate of soda. It is 
also essential in the manufacture of super-phosphate of 
lime, an article now extensively used in agriculture. 
Nitric and muriatic acids are produced through its 
agency from nitre and common salt. 

Nitrogen. 

Symbol, N; Equivalent, 14; Density, .97 

427. Description. — Nitrogen is a transparent gas, 
without taste or odor. It forms about four-fifths of the 
air we breathe. It occurs also in combination with 
other elements in a solid form. It is an essential ingre- 

426. What are the uses of sulphuric acid ? 427. What is nitrogen ? 
Where is it found ? 



NITROGEN. 201 

dient in all aniinal tissues, one-fifth of the weight of 
the dried flesh of animals being nitrogen. It is also 
found in many vegetable substances, and it enters into 
the composition of nitre and other salts. The gas 
emitted from the volcanoes of Europe is said to be 
principally nitrogen ; but carbonic acid (to be hereafter 
described) is discharged in great abundance from the 
active volcanoes of America. 

428. Preparation of Nitrogen. — Nitrogen is pre- 
pared from ordinary air by removing its oxygen. For 
this purpose a small portion of phosphorus is floated on 
a slice of cork upon water, and kindled, and a vial or a 
jar is inverted over it. As it burns J 14 
it abstracts the oxygen ; the water 
rises to take its place, and what is 
left of the air is nitrogen. The 
cork should be a little hollowed 
out, and chalk scraped into the 
cavity. Water must be poured into the saucer as the 
first portion rises into the bottle. The bottle is then 
cooled, either by water or long standing, and corked 
while yet inverted. It is then shaken, to wash the gas. 
A piece of phosphorus, of the size of a large pea, is 
sufficient for the preparation of half a pint of gas. 

429. Explanation. — The burning phosphorus selects 
all of the oxygen atoms in the air, and, by combining 
with them, converts them into solid particles of a cer- 
tain oxide of phosphorus called phosphoric acid. These 

428. How is nitrogen prepared ? 429. Explain the process. 




202 



PRINCIPLES OF CHEMISTRY. 



particles at first appear as a white smoke, and are after- 
ward dissolved in the water. 

430. Nitrogen may be procured in large quantities by 
passing a current of air, deprived of carbonic acid, 
over copper turnings heated to dull redness, when the 
copper will absorb the oxygen, and the nitrogen set 

115 




free may be collected over mercury, or over w r ater de- 
prived of air by boiling. To perform this experiment 
introduce copper turnings into a tube of porcelain, or 
hard glass, placed over a chafing dish. One extremity 
of this tube is connected with an apparatus designed to 
furnish a current of air, the other is connected with a 



430. How may nitrogen gas be procured in larger quantity ? 



NITEOGEN. 203 

curved tube communicating with a jar arranged to re- 
ceive the gas. The U-shaped tube seen in figure 115 is 
filled with pumice-stone saturated with caustic-potash 
to deprive the air of the carbonic acid which it con- 
tains. If we wish to obtain the gas entirely free from 
moisture the air should be passed through a second U- 
shaped tube filled with pumice-stone saturated with 
concentrated sulphuric acid. When the apparatus is 
thus arranged water flows from the stop-cock through 
the funnel into the jar and .drives the air it contains 
through the apparatus and pure nitrogen is obtained 
in abundance. This method should be employed in 
preference to all others where large quantities of nitro- 
gen are required. By measuring the amount of air 
driven through the apparatus and the nitrogen collected, 
the proportion of nitrogen in the air is easily estimated. 

431. Nitrogex extinguishes Flame. — If a burning 
taper be lowered into the bottle of nitrogen, as above 
prepared, it will be immediately extinguished. Flame 
is the brightness which accompanies active chemical 
combination, but here is nothing to combine. Nitro- 
gen is a sloth among the elements, possessing no degree 
of chemical activity. 

432. Principal Office of Nitrogen. — The princi- 
pal office of the nitrogen of the air is to dilute its oxy- 
gen. The latter, if pure, would soon consume our 
bodies as it hastens the combustion of a taper or other 
combustible. 

431. Does nitrogen extinguish flame ? Why ? 432. What is the prin- 
cipal office of nitrogen ? 



204 PRINCIPLES OF CHEMISTRY. 

433. The Atmosphere. — The air we breathe, and 
which, to the depth of fifty miles or more, forms the 
transparent envelope of the globe we inhabit, is a mix- 
ture of nitrogen and oxygen gases with aqueous vapor. 
It also contains small and varying proportions of car- 
bonic acid and ammonia. The growth of plants, the 
respiration of animals, the combustion of burning 
bodies, and other chemical operations upon the face of 
the earth's surface are continually effecting changes in 
the gases which compose- the atmosphere, yet these 
changes are so beautifully adjusted that the composition 
of the atmosphere remains unchanged from age to age. 

434. Proof that Air is a Mixtctre. — That air is a 
mixture, and not a chemical compound, is sufficiently 
evident from the fact that it possesses no new and 
peculiar properties different from those of its constitu- 
ents. It is further proved to be a mixture, from the 
fact that heat, which is the usual attendant on chemi- 
cal combination, is never occasioned when air is arti- 
ficially produced by the admixture of its constituents. 
Water absorbs the oxygen and nitrogen of the air in 
the same relative proportions that it would absorb each 
of those gases in a free state. The air expelled from 
rain water or melted snow by boiling contains one-third 
oxygen, while common air contains only one-fourth 
oxygen. This fact also shows that air is not a chemical 
compound but that the gases composing it are merely 
mingled mechanically. 

433. What is the composition of the air ? 434. How is it proved to be 
a mixture ? 



NITROGEN. 



205 



435. Use of Carbonic Acid and Ammonia in the 
Air. — Carbonic acid and ammonia, although present in 
the air in extremely small quantity, subserve the most 
important purposes in administering to the growth of 
plants. They constitute the gaseous food of all forms 
of vegetable life, as will be more fully explained in suc- 
ceeding chapters of this work. 

436. Analysis of the Air. — The method by which 
the relative amount of oxygen and nitrogen in the air 
is determined has been already given. On burning phos- 
phorus under a glass jar, as there described, the water 
is found to rise and fill a little more than one-fifth of 
the vessel, thereby indicating that one-fifth of the air 
which it contained was oxygen gas. The remaining 
four-fifths is nearly all nitrogen. In accurate experi- 
ments, a graduated tube is employed, instead of a jar 
or tumbler. It is not essential that the phosphorus 
should be ignited. With- 
out ignition, it will gradu- 
ally combine with all the 
oxygen, and remove it from 
the air contained in the 
tube. 

In order to determine the amount of aqueous vapor 
and carbonic acid in the atmosphere, a gallon, or other 
measured quantity of air, is drawn through tubes con- 
taining materials to absorb these substances. This 



116 




435. What purpose is served by its carbonic acid and ammonia ? 436. 
How is the proportion of nitrogen determined? How is the amount of 
carbonic acid water and ammonia determined ? 



206 



PRINCIPLES OF CHEMISTRY. 



117 



quantity is known by the increased weight of the tubes 
after the experiment is completed. 

437. The Apparatus described. — The apparatus 
used in the experiment is represented in the last figure. 
It consists of a bottle or small cask, filled with water 
and provided with a cock below. The cock is turned, 
and as the water flows out, air flows in through the tube 
to take its place. The quantity of air that has passed 
through the tubes is known by the quantity of water 
that has flowed out from the cask. The materials em- 
ployed in the tubes are pumice stone drenched with oil 
of vitriol, in the first, to absorb the water ; and caustic 
potassa, in the second, to retain the carbonic acid. In- 
stead of straight tubes it 
is found more conven- 
ient to employ the series 
of U-shaped tubes and 
bulbs shown in figure 
117. A and D are filled 
with pumice saturated 
with oil of vitriol, B is 
partly filled with a concentrated solution of caustic pot- 
ash, and C is filled with fragments of fused potash. The 
acid in D absorbs all the moisture from the air to be ana- 
lyzed and the acid in A prevents the access of moisture 
from the cask of water or aspirator towards which the 
air is drawn. The increased weight of B and C shows 
the amount of carbonic acid in the air drawn through the 
the apparatus. The method for determining the amount 

437. Describe the apparatus used in this analysis. 




NITRIC ACID. 207 

of ammonia in the atmosphere is essentially the same, 
muriatic acid being used as the absorbent. 

438. Proportional Composition of the Air. — The 
proportions of the four constituents of the air above 
mentioned, as obtained by the method just described, 
are about 21 per cent, of oxygen, 79 of nitrogen, 
^Vo-th- of carbonic acid, and T o ooV o o o th of ammonia. 
The proportion of aqueous vapor is extremely variable. 
That of carbonic acid and ammonia is also variable to 
a considerable extent. 

Nitric Acid. X0 5 = 54. 

AquaFortis; HO J N0 5 ==63. 

439. Description. — Nitric acid is a thin, colorless and 
intensely acid fluid. It corrodes metals instantaneously, 
with the evolution of deep red vapor. It is composed 
of nitrogen and oxygen, in the proportion of one atom 
of the former to five of the latter. It contains, in 
addition, water, with which it is chemically combined. 
It is possible to make it anhydrous, or free from water, 
but such an acid is never used. 

440. Preparation. — Nitric acid exists in a dormant 
state in ordinary saltpeter. Its affinities being entirely 
satisfied by the potassa with which it is combined in 
that substance, it lies there perfectly inactive. Sulphu- 
ric acid being stronger, has the power of taking its 
base, and expelling the acid in the form of vapor. 

438. What are the proportions of the different constituents of the at- 
mosphere? 439. What is nitric acid ? 440. How is nitric acid prepared ? 



208 



PRINCIPLES OF CHEMISTRY. 




119 



Saltpeter (nitrate of potash) with an equal weight of 
sulphuric acid is heated in a retort, connected with a 

a receiver, kept 
cool by a stream 
of water drop- 
ping upon a cloth 
spread over it as 
as shown in fig- 
ure 118. 

For the purposes 
of experiment ni- 
tric acid may be prepared by placing the saltpeter and 
oil of vitriol in a test tube heated over a lamp as in 

figure 119, while the acid 
fumes may be collected 
in a vial or flask. It is 
necessary to keep the vial 
covered with porous paper 
or cloth, and to moisten 
it frequently in order to 
maintain its coolness. 
441. Oxidation of Metals. — If a little nitric acid 
is poured upon a copper coin, placed in a capsule or 
saucer, the coin will immediately begin to dissolve. It 
is not, strictly speaking, the metal which dissolves. 
One portion of the acid first converts the metal into 
oxide, by giving it part of its own oxygen. It thereby 
destroys itself, while another portion of undecomposed 
acid dissolves the oxide which is formed. One portion, 




441. What effect has nitric acid on metals ? 



NITRIC ACID. 



209 



in reality, sacrifices itself to satisfy the appetite of the 
other. Most other metals are similarly acted on by 
nitric acid. 

442. Oxidation without Solution. — Nitric acid 
oxidizes tin and antimony but does not dissolve them. 
The experiment Trill be best made with tin-foil. After 
the action of the acid, it will be found converted into a 
white powder. Gold and platinum are neither dissolved 
nor oxidized by nitric acid. 

443. Nitric Oxide.* — The vapors which are given 
off in the experiment with copp'er described in Section 
441 are nitric oxide, changed by the ah- into which 
they rise. The nitric oxide is, so to speak, the frag- 
ment of nitric acid, which is left after three atoms of 
its oxygen are abstracted. Rising into the air, it com- 
bines with oxygen enough partly to supply the place of 
that it has just lost, and is thus converted into red 
fumes of peroxide 
of nitrogen con- £ x 
taining four at- 
oms of oxygen. 
This compound is 
also called hypo- 
nitric acid. 

444. Prepara- 
tion. — Bin oxide 
of Nitrogen or 
Nitric Oxide may 

442. How does nitric acid act on tin ? 443. What is nitric oxide ? 




* It will be observed that the term oxide is sometimes applied to compounds of the 
non-metallic substances with oxygen. (See Chapter III, Inorganic Chemistry.) 



210 PRINCIPLES OF CHEMISTRY. 

be obtained by pouring nitric acid through the funnel, 
£, upon fragments of copper contained in the flask, a, 
as shown in figure 120. The gas escapes through the 
tube, <?, and may be collected over water. This gas has 
a strong disagreeable odor, and it extinguishes burning 
bodies, as a lighted taper or phosphorus when plunged 
into it. This gas retains its own oxygen with great 
tenacity and greedily absorbs more from the atmos- 
phere. When a jar partly filled with this gas is raised 
from the water bath and atmospheric air is admitted, 
dense red fumes appear, which are peroxide of nitrogen, 
containing four atoms of oxygen to one atom of nitro- 
gen. These red fumes are quickly 
absorbed by water. This experi- 
ment may be performed with en- 
tire satisfaction by means of the 
simple apparatus shown in figure 
121. The peroxide of nitrogen 
may be reduced to the liquid 
form at a low temperature. It is readily decomposed 
by oxidizable metals, and, as it readily parts with oxygen, 
it is a powerful oxidizing agent. 

445. Protoxide of Nitrogen or Laughing Gas. — 
This gas is obtained by heating nitrate of ammonia in 
a flask over a lamp. The salt first melts and is then 
decomposed and converted into water and protoxide 
of nitrogen, which contains one atom of nitrogen united 
to one atom of oxygen. This is a colorless gas, sweet- 
ish to the taste, and it imparts its flavor to water in 

444. How is binoxiclc of nitrogen prepared ? 445. How is protoxide of 
nitrogen prepared? Describe the properties of this gas. 




NITRIC ACID. 



211 




which it is sparingly soluble. A candle recently ex- 
tinguished is re- 
lighted with near- 
ly the same facil- 
ity as in oxygen. 
Other bodies burn 
in this gas with 
greater facility 
than in common 
air, showing that 
its elements are 
united by a feeble 
affinity. 

When this gas is inhaled from a large bladder or gas 
bag it produces exhilirating effects from which it has 
received the name, laughing gas. Impurity of material 
or excess of heat cause the production of other delete- 
rious gases mingled with the protoxide of nitrogen, from 
the inhalation of which serious accidents have some- 
times q^curred. In view of these facts the preparation 
and inhalation of laughing gas 
is not to be recommended to the 
student. 

446. Combustion by Nitric 
Acid. — As nitric acid contains 
much oxygen, combustion by its 
means would seem to be a very 
probable result. To prove that 
it has this effect, boil strong 




446. How may combustion be effected by nitric acid 1 




212 PRINCIPLES OF CHEMISTRY. 

nitric acid in a test-tube, the mouth of which is filled 
with hair. As the vapors pass through they will cause 
it to smoke, and, if the acid is sufficiently strong, pro- 
duce ignition. 

447. Combustion of Phosphorus. — Phosphorus is 

124 readily ignited by throwing it 

upon nitric acid. If the acid is 
not very strong, it must be previ- 
ously heated. Particles of phos- 
phorus scarcely larger than mustard seed should be 
used in this experiment. 

448. Destruction of Organic Tissues. — Strong 
nitric acid destroys all organic tissues and forms a 
powerful cautery much used in medicine. It also gives 
a yellow color to the nails and skin even when diluted, 
and it has the same effect upon wool; the orange pat- 
terns upon woolen table covers are produced by the 
same means. Other uses of nitric acid are mentioned 
in the chapter on Organic Chemistry. 



Phosphorus. 

Symbol,?.', Equivalent, 31 ; Specific Gravity, 1.83. 

449. Description. — Phosphorus is a substance remark- 
able for its power of emitting light in the dark. It is a 



447. Describe the experiment with phosphorus? 448. What is the 
effect of nitric acid upon organic substances ? 449. What is phosphorus ? 
Where does it occur ? 



PHOSPHORUS. 213 

wax-like and nearly colorless solid, readily ignited by 
heat or friction.* It is insoluble in water (and hence 
nearly tasteless,) but it is soluble in ether and in oils. 

Phosphorus is never found uncombined, but it occurs 
in the form of phosphate of lime in the mineral called 
apatite, in primitive and volcanic rocks, from the 
gradual decomposition of which it finds its way into the 
soil. It is taken up by many plants and accumulates 
in their seeds. In this form it becomes the food of 
animals, and forms an important element in the compo- 
sition of bones. It is also an essential ingredient in 
the substance of the brain and nerves. 

450. Preparation. — Phosphorus is prepared from 
bones. These are composed, principally, of gelatine 
and phosphate of lime. The individual constituents 
are gelatine, lime, oxygen and phosphorus. To obtain 
the phosphorus, all the rest are to be first removed. 
Fire removes the gelatine, oil of vitriol the lime, and 
charcoal the oxygen. 

The bones having been previously burned, the 
ground ash is mixed with dilute sulphuric acid and 
water, and, after several hours, filtered. Sulphuric 
acid unites with a considerable part of the lime, form- 
ing an insoluble sulphate, and the phosphoric acid re- 
mains combined with only a small portion of the lime 

450. How is it prepared ? Give the complete process 



This is a very dangerous substance to handle producing very obstinate and 
severe burns when it takes fire upon the hands, hence it should always be cut under 
water and every particle not used should be immediately returned to a bottle of 
water protected from light. 



214 



PRINCIPLES OF CHEMISTRY. 




trr.-f 



in a form called superphosphate of lime. The solution 
containing this superphosphate is then mixed with char- 
coal, and after being carefully dried, it is heated in an 
125 - earthen or iron retort, A, con- 

nected with a copper receive!', 

B, containing water, and fur- 
nished with an escape tube, 

C. Several such retorts are 
placed side by side in a fur- 
nace, n, where they can be 
conveniently heated. The car- 
bon takes the oxygen from a 

large portion of the phosphoric acid, and passes out of 
the retort with it, as gaseous carbonic oxide. The 
phosphorus which is thus set free, being vaporized by 
the heat, is also expelled, but is converted into solid 
phosphorus by the cold water into which it passes. 
The gas produced by the process bubbles through the 
water and escapes, while the phosphorus is hardened 
by it and remains. The mass thus obtained is melted 
under water and run into moulds. 

In preparing phosphorus in the large way, a number 
of retorts are placed in the same furnace. 

451. Phosphorescence. — This term is applied to the 
luminous appearance of sea-water when agitated, and 
to other faint light unaccompanied by perceptible heat. 
It is observed when an ordinary friction match is rub- 
bed upon the hand in the dark. The light in the lat- 



451. What is phosphorescence ? 



PHOSPHORUS. 215 

ter case is owing to a slow combustion of phosphorus, 
which takes place without kindling. The product of 
the combustion, is a white powder, called phosphorous 
acid, which soon becomes liquid, by absorbing moisture 
from the air. 

The phosphorescence of sea-water has been supposed 
to be owing to the liberation of phosphorus by the de- 
cay of jelly-fish or blubber so abundant in the ocean. 
Many sea-fish emit light in the dark soon after death if 
placed in saline solutions, but the effect ceases when 
putrefaction commences. Many bodies containing no 
phosphorus emit light in the dark when there is no 
apparent oxidation. The cause of phosphorescence is 
but imperfectly understood, though it is believed to be 
generally due to the slow oxidation of the phosphores- 
cent matter. 

452. A harmless Fire. — By agitating phosphorus 
with ether, a small portion of the former substance is 
dissolved. This solution, if rubbed upon the face and 
hands, makes them luminous, in the dark. This is an- 
other case of phosphorescence. A piece of phosphor- 
us of the size of a pea is amply sufficient for the ex- 
periment. 

453. Combustion under "Water. — Phosphorus may 
be burned under water by the help of substances rich 
in oxygen. Place a few scales of chlorate of potassa, 
and a bit of phosporous of the size of a pea, at the bot- 



452. How may a harmless fire be produced? 453. How may phos- 
phorus be burned under water ? 



216 PRINCIPLES OF CHEMISTRY. 

torn of a wine glass previously filled with water. Par- 
tially fill the bowl of a pipe with oil of vitrol, and drop 
126. it in small portions on the mixture, bringing 
<4 the pipe stem, each time, close to the bottom 

^==1 of the glass. As soon as the stronger acid 
■^^ is applied, chloric acid, containing much oxy- 

<^S^- gen, is liberated and decomposed, and the 
phosphorus inflamed. A similar combustion of phos- 
phorus, by means of nitric acid has already been de- 
scribed. In both cases the result is the production of 
phosphoric acid. 

454. Friction Matches. — Great quantities of phos- 
phorus are annually consumed in the manufacture of 
friction matches. For this purpose the phosphorus is 
first intimately mixed with a hot solution of glue, or 
gum, to which saltpetre is added, and the paste thus 
formed is frequently colored with vermilion or Prus- 
sian blue. The match splints are first dipped in melt- 
ed sulphur, when cold they are dipped in the phos- 
phorus paste, and after being thoroughly dried in an 
oven heated by steam they are packed in boxes con- 
venient for use. 

455. Red Phosphorus. — When phosphorus is sub- 
limed in a perfect vacuum, or surrounded with an 
atmosphere of carbonic acid or hydrogen, it becomes 
changed in color and properties. It then assumes 
the form of red scales, acquires a density of 1.94, and 
instead of fusing at 111° F., as in the ordinary con- 

454. What is said of friction matches ? 455. What is said of red phos- 
phorus. 






ARSENIC. 217 

dition, it may be heated to 392° without becoming 
luminous, and it requires a temperature of 500° to 
melt it, but at this temperature it is reconverted 
into the ordinary form. While the ordinary form of 
phosphorous is a rank poison, and highly inflamma- 
ble, the red phosphorus, if perfectly pure, is quite 
inert, and but slightly inflammable. For this reason 
efforts have been made to substitute the red phos- 
phorus in the manufacture of matches, but owing to 
the difficulty of preparing the red phosphorus without 
some mixture of the ordinary form, the experiments 
have as yet been attended with but partial success.* 

Arsenic. 

Symbol, As; Equivalent, 15; Specific gravity, 5.8. 

456. Description.— Arsenic is a grey substance, of 
metallic luster, and for this reason commonly classed 
among the metals. On the other hand, in view of the 
compounds which it forms, and especially in view of 
the fact that its oxygen compounds are acids, and not 
oxides, it is more properly classed among the metalloids. 
Its analogies to phosphorus are most striking, and it is 
for this reason here introduced, in immediate connec- 
tion with that element. 

456. Why is arsenic introduced among the metalloids ? 

• ! The manufacture of matches is attended with considerable danger both on 
account of the inflammable nature of the materials employed, arid also from the fact 
that tbe vapor of phosphorus attacks the carious teeth of the workmen, and pro- 
duces a disease whioh extends to the jaw-bones, producing extreme suffering and 
often terminating in death. 



218 PRINCIPLES OF CHEMISTRY. 

457. Analogies to Phosphorus. — Arsenic unites 
with oxygen in the same proportions as phosphorus, 
forming similar acids. These in turn form salts resem- 
bling each other most perfectly in external appearance 
and in crystalline form. It also combines with three 
atoms of hydrogen to form arseniuretted hydrogen, a 
gas analogous to phospuretted hydrogen, to be hereafter 
described. Of the two principal oxygen compounds of 
phosphorus, the higher or phosphoric acid is the more 
important, and w r as therefore more particularly consid- 
ered. On the other hand, the lower or arsenious acid 
is the more important of the acids of arsenic. 

458. Preparation. — Metallic arsenic is sometimes 
found native ; but more frequently it is combined with 
other metals, as iron, nickel, cobalt, copper or tin. It 
is obtained in large quantities from an ore called Mis- 
picket, which is an arsenical sulphuret of iron. It is 
also obtained from the arsenical sulphurets of other 
metals. The arsenical sulphurets are roasted in furna- 
ces having flues connected with large chambers. The 
sulphur and arsenic are burned in the furnace and pass 
off in the form of oxides. The oxide of sulphur (sul- 
phurous acid) being very volatile passes off through the 
chambers and escapes into the open air, while the less 
volatile oxide of arsenic (arsenious acid) is condensed 
in the chambers to which it is conducted forming a 
thick vitreous crust, which is removed by workmen 
encased in leather to protect them from the corrosive 



457. In what respect do phosphorus and arsenic resemble each other ? 
458. How is arsenic prepared ? 




AESEKIOUS ACID. 219 

action of the poisonous material they are handling. 
They breathe through wet cloths, to protect their lungs 
from the poisonous dust, and they look through glazed 
openings in the mask which covers the face. The crude 
arsenious acid thus obtained is purified by resublima- 
tion and forms the white arsenic or arsenious acid of 
commerce. The sublimed arsenious acid is then pow- 
dered and heated with a large pro- 
portion of carbon, as in the case of 
phosphorus, before described. Be- 
side mixing with carbon, it is best, 
also, to cover with the same material, 
and heat from above, downwards. 
The metal passes off as vapor, and condenses in the 
cooler part of the tube, or other vessel in which the 
experiment is performed, as a steel grey incrustation. 
Arsenic is very volatile, forming a colorless vapor ten 
and a-half times as heavy as air, which is easily recog- 
nized by its powerful alliaceous odor. Arsenic may be 
melted in close vessels but when heated in the open air 
it volatilizes before it melts. 

Arsenious Acid. As0 3 

459. Ratsbane. — The ordinary white arsenic of the 
shops, also known as ratsbane, is a white and nearly 
insoluble substance, possessed of a slightly sweetish 
taste. It is not properly arsenic, but arsenious acid. 
It contains three atoms of oxygen to one of metal. 

459. What are the properties of arsenious acid ? 



220 PRINCIPLES OF CHEMISTEY. 

Although sweet, it is called an acid because it possesses 
the chemical characteristic of an acid, viz. : the capa- 
city of uniting with bases to form salts. Arsenious 
acid is the compound obtained in the first stage of the 
process for manufacturing metallic arsenic, as above 
described. 

460. Arsenic Acid, AsCh. — Is another oxide of 
arsenic containing five atoms of oxygen to one atom 
of the metal. Its composition is analogous to that of 
phosphoric acid. 

481. Other Compounds of Arsenic. — Sulphur and 
arsenic may be melted together in all proportions, but 
they form several well defined compounds, the most 
important of which are the bisulphide of arsenic called 
realger, and the tersulphide or orpiment. Realger con- 
tains one atom of arsenic united with two atoms of 
sulphur. It is occasionally found in the form of ruby- 
red crystals. It is sometimes used as a pigment. It 
forms one of the ingredients of white Indian fire, which 
is often used as a signal light. This compound consists 
of 7 parts of sulphur, 2 of realger, and 24 of nitre. 

Orpiment is a yellow compound of sulphur and 
arsenic containing three atoms of the former and one 
of the latter. A mixture of arsenious acid and orpi- 
ment forms the beautiful pigment known as King's 
yellow. 

Arseniuretted hydrogen is a gaseous compound con- 
taining one atom of arsenic united with three atoms of 

460. What is arsenic acid ? 461. What other compounds of arsenic are 
worthy of special notice ? 



AESENIOTS ACID. 221 

hydrogen. It is a highly poisonous gas of great inter- 
est in chemical analysis, and especially in a forni in 
which arsenic is obtained in medico-legal investigations. 
This gas is formed when arsenic or arsenions acid is 
thrown into a bottle containing zinc and chlorohydric 
acid. It burns with a bluish white flame which de- 
posits metallic arsenic upon cold bodies, like porcelain, 
held in the flame, and white arsenic (arsenious acid) 
upon those held above. 

462. Properties of Compoetstds of Arsexic. — Ar- 
senic forms with most of the metals alloys, which are 
brittle and easily fusible, hence it becomes important 
that such metals as iron copper and zinc should be 
thoroughly purified from arsenic. 

All the soluble compounds of arsenic are highly 
poisonous, and often prove destructive of animal life. 
Paper hangings, ornamented with the beautiful pig- 
ment known as Scheele's green (an arsenite of copper), 
produce serious disease in the occupants of rooms where 
they are used. Arsenic preserves animal substances 
from decay, and also by its poisonous properties pro- 
tects them from the ravages of insects. A few grains 
of white arsenic added to bookbinder's paste preserves 
the books from the ravages of insects in hot climates. 
Arsenical soap is employed by the taxidermist to pre- 
serve the skins of stuffed birds and other small ani- 
mals.* 

462. "What are the properties of compounds of arsenic ? 



* Arsenical soap is prepared by mixing 100 parts of hard soap, 100 parts of arsen- 



222 PRINCIPLES OF CHEMISTRY. 

463. Arsenic as a Poison was formerly much em- 
ployed for criminal purposes. But the certainty of 
its detection, and the entire demonstration of its pres- 
ence in the body after death, or in materials which 
have been ejected from the stomach, now strikes a just 
terror into the minds of those who would otherwise be 
tempted to use it for evil purposes. 

464. Antidotes for Arsenic. — The best antidote 
for arsenic is the hydrated sesquioxide of iron in the 
moist state, which forms with arsenious acid an insolu- 
ble arsenite of iron. Pure calcined magnesia may also 
be used for the same purpose. Either of these remedies 
may be taken freely as an antidote to arsenic. The 
white of eggs, milk, and sugar are also good remedies, 
and should be taken in considerable quantity when 
arsenic has been swallowed. If the poison can be re- 
moved by vomiting that is always the first remedy, and 
the others may be given afterwards. 

465. Detection of Arsenic. — !N"o one but a profes- 
sional chemist should undertake the detection of arsenic 
in criminal cases, involving, as it does, the issues of life 
and death. ]STo one else, indeed, can be qualified to 

463. *What fact tends to prevent the use of arsenic for criminal purpo- 
ses ? 464. What is the antidote for arsenic ? 465. What is said of its 
detection ? 

ions acid, 36 carbonate of potash, 15 camphor, and 12 of quick-lime. The soap is to 
be scraped and dissolved in a little water with a gentle heat, then add the potassa 
and the lime, and mix all well together. The arsenious acid should then be added 
gradually, and well incorporated, and, when the mixture is cold, the camphor, pre- 
viously dissolved in a small portion of alcohol, is to be thoroughly mixed with the 
compound. A portion of this soap, dissolved in water, applied with a brush to the 
objects to be preserved, effectually destroys all insects and their eggs.— Dumas. 



AKSENIOITS ACID. 223 

guard, with, certainty, against the presence of arsenic in 
the chemicals which are used in the process, or in other 
respects, to bring the inquiry to that point of absolute 
demonstration, which is always required in judicial in- 
vestigations. But the methods of detection, being sim- 
ple, and a subject of interesting and instructive experi- 
ment to the student, will be briefly described in the 
paragraphs which follow. 

If a few drops of a solution of chloride of arsenic* be 
added to the liquid from which hydrogen is being 
evolved from a vial, by the ordinary process, the nas- 
cent hydrogen decomposes the chloride of arsenic and 
carries off the metal in the form of a gas. On subse- 
quently kindling the hydrogen jet, and bringing down 
upon it a cold white surface, like that of 128. 

a plate or saucer, the metal is again given 
up, and reveals itself as a brownish black 
and highly lustrous stain. The process 
may be conducted in an ordinary vial, to 
which a pipe stem, or glass tube has been 
fitted, by the method before described. 

In cases of suspected poisoning the con- 
tents of the stomach are subjected to some process to 
destroy all the organic matter, and bring the whole 
into a state of solution. After filtering the suspected 
liquid, it is acidulated with muriatic acid, and submit- 
ted to a test like that above described, in an apparatus 

How is arsenic detected? 




* Such a solution is prepared by dissolving white arsenic in hydrochloric acid. 



224 



PRINCIPLES OF CHEMISTRY. 



especially fitted for the purpose. The amount of 
arsenic in such cases is usually small, and special pre- 
cautions are required to exhibit the characteristic re- 
actions with the smallest appreciable quantity of the 
poison. 

129. 




In the two-necked bottle, figure 129, are placed gran- 
ulated zinc and dilute sulphuric acid ; the bulb, &, is 
to condense the moisture, and the tube CaCl, is loosely 
filled with chloride of calcium to absorb the particles 
of fluid that would otherwise be carried over ; a tube of 
hard glass, c, made without lead, is placed over a dish 
of burning charcoal. If, after a few minutes, the tube 
is not soiled, and the saucer held in the flame of the 
burning hydrogen is not tarnished, the apparatus and 
materials for making hydrogen are known to be free 
from arsenic. The suspected liquid is then poured 
through the funnel, #, when, if arsenic is present, a 
metallic ring will soon appear in the capillary tube be- 
yond the screen, s, or if the fire is removed, and the 
escaping jet is inflamed, a tarsh, or stain, of metallic 
luster will appear upon the saucer held in the flame. 



ARSE N 10 US ACID. 225 

The above method of detection is called Marsh's 
test. In a case of suspected murder by poison, the mo- 
ment of the introduction of the pure porcelain into the 
flame becomes one of the most intense interest. The 
gathering stain is at once the emblem of guilt and sen- 
tence of ignominous death. 

486. Explanation. — In the above experiment nas- 
cent hydrogen effects the decomposition of the acid by 
a double action ; on the one hand uniting with the 
metal to form arseniuretted hydrogen, which escapes, 
and, on the other hand, with its chlorine to form hydro- 
chloric acid, which remains behind. The mirror of 
metal is deposited upon the plate or saucer, because 
the introduction of the cold body into the flame, so 
lowers its temperature that the metal itself cannot 
burn. If the jet of gas is left to burn without inter- 
ference, both of its constituents are consumed together, 
and the flame assumes a blue color, from the burning 
arsenic. 

467. Distinction between Arsenic and Antimony 
Stains. — If, in testing for arsenic, by the method above 
described, a metallic spot is obtained, the evidence of 
the presence of arsenic is not entirely conclusive. A 
solution of antimony, if substituted for arsenic in the 
experiment, will give rise to the production of some- 
what similar stains. But the experimenter will find, 
on comparing the two kinds of spots, that they are 
quite different in appearance. Those of antimony are 

466. Explain the above process. 467. How are arsenic and antimony 
stains distinguished? 



226 PRINCIPLES OF CHEMISTRY. 

of deeper black, and fainter luster. Again, those of 
arsenic are much more readily removed by heat. 
" Chloride of soda," is a still more conclusive means of 
distinguishing them. A solution of this substance will 
dissolve the arsenic stains, while it leaves those of anti- 
mony unaffected. The " chloride of soda," to be used 
in the experiment, is prepared by adding an excess of 
carbonate of soda to a solution of " chloride of lime," 
nd then filtering the liquid. 

468. Additional Tests tor Arsenic. — A second 
test has already been given in the paragraph on the 
preparation of metallic arsenic, to which the student is 
referred. The formation of a yellow precipitate, on the 
addition of hydro-sulphuric acid to a solution, also 
renders it highly probable that arsenic* is present. If 
on drying the precipitate, and heating it with a mixture 
of cyanide of potassium and carbonate of soda, a metal- 
lic mirror is obtained, the inference of the presence of 
arsenic is confirmed. The process is to be conducted 
as directed in paragraph 458. In this experiment, the 
cyanide of potassium has the effect of retaining the 
sulphur, while it allows the volatile arsenic to pass and 
deposit above. 

469. Still another evidence of the presence of arsenic, 
is afforded in the characteristic garlic odor which is 
emitted by the flame produced by burning arsenic, in 
the experiment previously described, called Marsh's 



468. Mention some additional tests for arsenic ? 469. What is 6aid of 
the garlic odor f 



AESENIOUS ACID. 227 

test. The same odor is also obtained on sprinkling a 
little arsenions acid upon burning charcoal.* 

470. Preparations FOE the Aksenio Test. — Before 
proceeding with the chemical experiments for the detec- 
tion of arsenic, some preliminary labor 
is commonly required, to bring the 
material to be tested into proper form. 
It commonly consists of matters which 
have been ejected from the stomach, or 
of the contents of the stomach itself. 
If the student wishes to begin at this 
point in his experiments, he may add a small portion 
of arsenic to some bread and water and proceed with 
this paste in his investigation. This mixture is to be 
diluted with water and saturated with chlorine, as in 
the process for preparing a solution of this gas. Chlo- 

470. Mention the preparations for the arsenic test ? 




* The Subtlety of Poisons— At a recent discussion before the Society of Arts 
in London on the detection of arsenical poisoning, Dr. Letheby traced the progress 
of toxicological research from the trial of Donald, in 1815, up to the present time. 
A little while before that period, ten grains of arsenic were required to make 
a metallic test satisfactory in a court of law. Afterwards Dr. Black improved the 
process till he could detect the poison if he had one grain to operate upon. It was 
then thought a marvel of toxicological skill when Dr. Christison said he only re- 
quired the sixteenth of a, grain ; but now we can trace the presence of the £50,000,- 
COOth of a grain of arsenic ! It is to be feared that the detection of this particular 
poison has reached an almost dangerous degree of delicacy, and extreme caution is 
necessary in examination for its criminal administration. We live surrounded by 
means of unconsciously absorbing traces of arsenic; we breathe arsenicated dust 
from the green wall papers of our rooms ; the confectioners supply it wholesale in 
their cake ornaments and sweetmeats ; the very drugs prescribed for our relief are 
tainted with arsenic ; nay, more, even our vegetable food, as Professor Davy has 
lately poioted out, may be contaminated with arsenic ; and there is probably no 
drinking water containing iron without a trace of arsenic as well. The poison may 
thus be stored up in the system until in the course of years, the amount becomes 
appreciable. 



228 PRINCIPLES OF CHEMISTRY. 

rine has the effect of destroying a certain portion of 
the organic matter, and rendering the rest floculent, so 
that the liquid may be easily separated from it by filtra- 
tion. It also brings the arsenic perfectly into solution, 
as a chloride. This solution is then filtered and treated 
as directed in the preceding paragraphs. 

471. Arsenic Eaters of Austria.- — In the moun- 
tainous portions of Austria, bordering on Hungary, the 
peasantry are given to the strange habit of eating arse- 
nic. It is said to impart a fresh, healthy appearance to 
the skin, and also to make respiration freer when ascend- 
ing mountains. Those who indulge in its use com- 
mence with half a grain, and gradually increase the 
dose to four grains. If this habit is regularly indulged, 
its injurious effects are said to be long retarded. But 
as soon as the dose is suspended, the symptoms of pois- 
oning by arsenic immediately manifest themselves. 

Carbon. 

Symbol, C ; Equivalent, 6 ; Specific Gravity, 3.5. 

472. Common Forms of Carbon. — Carbon in the 
form of coal is a well known black and brittle solid. 
Bituminous and anthracite coals exist in immense 
quantities buried in the earth in various countries. 
Bituminous coal differs from anthracite in that it con- 
tains a considerable quantity of volatile oil. Anthra- 
cite is supposed to have been deprived of volatile oil by 

471. What is said of the arsenic eaters of Austria ? 472. What are the 
common forms of carbon ? 



CARBON. 



229 



the action of subterranean heat which has accumulated 
those vast stores of rock oil which are becoming of so 
much importance in commerce. When bituminous coal 
is heated in retorts for the purpose of obtaining illumi- 
nating gas there is left a loose brittle residue, called 
coke, which differs from anthracite only in form. Char- 
coal and plumbago are other common forms of carbon. 
473. Preparation of Charcoal. — Charcoal is com- 
monly made by burning wood in large heaps or pits 
covered with earth or sod. The arrangement of these 

181 




heaps is shown in the accompanying figures. Upright 
bundles of wood in the center serve the purpose of a 



473. How is charcoal prepared ? 



230 PRINCIPLES OF CHEMISTKY. 

chimney and air is admitted by convenient openings 
around the base. The whole pile should be thoroughly 
dried before burning as it makes from 15 to 25 per 
cent, more charcoal than when green wood is employed. 
In charring green wood much of the fuel is consumed 
in driving away the moisture and other gases which 
combine with it. When the pile is sufficiently charred 
the openings are closed and the fire being smothered 
dies out. The whole operation requires from two to 
four weeks for its completion. Charcoal for the manu- 
facture of gunpowder and for some other purposes is 
prepared in iron retorts. 

474. Smoke is carbon in a finely divided state carried 
upward by the heated vapor and gases which escape 
during combustion. The formation of smoke depends 
upon imperfect combustion, occasioned by insufficient 
supply of air in the burning fuel. To prevent the for- 
mation of smoke it is necessary to supply the fuel in 
small quantities, so arranged that the air may have 
ready access to all parts. A strong blast of air driven 
through the fuel facilitates combustion and prevents the 
formation of smoke. It is much easier to prevent the 
formation of smoke than to consume it after it is 
formed. 

475. Lampblack — Ivory-black. — Lampblack is a 
form of carbon prepared by collecting the smoke of 
rosin or oil in chambers constructed for the purpose. 
It consists of unburned particles of carbon. It is used, 

474. What is smoke ? and how may its formation be prevented ? 475. 
What is lampblack ? What is ivory black ? 



CARBON. 231 

extensively, as a pigment. India ink is made from the 
finest quality of lampblack. Bone black or ivory black 
is made by heating bones in closed vessels. It is a sort 
of charcoal produced from the gelatine of bones. 

476. Purifying Properties of Charcoal. — Char- 
coal absorbs gases, and retains them in its pores, in 
large quantities. Tainted meat, and musty grain, inti- 
mately mixed with it, become sweet. The charcoal 
removes the unpleasant gases proceeding from them. 
The absorbent power of charcoal may be illustrated, by 
holding a paper moistened with ammonia, in a vial, 
until the air within it has acquired a strong ammoniacal 
odor. On afterward introducing some powdered char- 
coal and shaking the vial, the odor will be removed. 

477. Preservative Properties of Charcoal. — 
Charcoal may be used as a preventive, as well as a cor- 
rective of decay. Posts, if charred at the bottom be- 
fore they are set, are rendered more durable. Water 
will keep longer in vessels. charred on the inside than 
in those which have not been thus prepared. The de- 
cay of meats and vegetables is retarded by packing 
them in charcoal. Charcoal is itself one of the most 
unchangeable of substances. "Wheat and rye charred 
at Herculaneum 1800 years ago, still retain their per- 
fect shape. 

478. Decolorizing Effects of Charcoal. — Char- 
coal has, also, the effect of removing coloring matters, 



476. Describe the purifying properties of charcoal. 477. niustrate the 
preservative properties of charcoal. 478. Describe its decolorizing 
power. 




232 PRINCIPLES OF CHEMISTRY. 

and bitter and astringent flavors from liquids. Thus, 
ale and porter lose both color and flavor by being fil- 
tered through charcoal. Sugar refiners take advantage 
131. of this property in decolorizing their brown 
syrups. Animal charcoal or bone black is 
best adapted to these uses. As an illustra- 
tion of the decolorizing effect of charcoal, let 
water, colored with a few drops of ink, be fil- 
tered through bone black. The color will 
be found to disappear in the process. 

479. The Diamond is the purest form of carbon, 
being often perfectly transparent. It is found in the 
form of an octahedron — a solid, formed of tw^o square 
pyramids joined together by their bases. It is also 
found in other secondary forms derived from the octa- 
hedron by beveling its edges and removing its solid an- 
gles. The figure shows a common form, 
bounded by 24 triangular faces. The sur- 
face of diamonds is frequently, more or 
less, rounded by the action of sand and 
gravel, with which they have been trans- 
ported. 

480. Uses of Diamonds. — The diamond is the hard- 
est substance known. Its most important use is for 
cutting sheets of glass. For this purpose a natural 
angle is employed, set in a convenient handle. The 
diamond can only be cut or abraded by its own dust ; 
stones of inferior quality being broken up for this pur- 

479. What is the purest form of carbon ? 480. What are the uses of 
the diamond ? 





CARBON. 233 

pose. Diamonds are cut for jewelry in two forms 
called the rose, figure 134, and the 
brilliant, figure 133. By cutting, 
the weight of the diamond is di- 
minished nearly one-half. 

481. Value of Diamonds. — The diamond is the 
most costly of all gems. The weight of diamonds is 
estimated in carats.* Small diamonds, unfit for cut- 
ting, such as are used by glass-cutters and glaziers, are 
worth from two and a half to four dollars per carat, and 
still smaller ones are worth less ; they are now em- 
ployed by lithographers for their engravings and etch- 
ings. 

A diamond cut for setting, weighing one carat, is 
worth from 36 to 50 dollars, depending on its color and 
transparency. The value of diamonds increases in pro- 
portion to the square of the weight. A diamond weigh- 
ing 10 carats is worth 100 times as much as a diamond 
of one carat, and for diamonds weighing more than 100 
carats, when properly cut, the estimated value is much 
greater than this proportion would indicate. The great 
diamond belonging to the crown jewels of England, 
called the Kohinoor (or Mountain of Light), weighs 
103 carats, and is valued at from three to ten million 
of dollars. There are only about thirty diamonds 
known which weigh over 100 carats each. The finest 
diamonds are obtained from Golconda in India. But 

481. How is the value of diamonds estimated? 



The carat is a weight of four grains. — Feuchtwanger's " Treatise on Gems." 




234: PRINCIPLES OF CHEMISTRY. 

diamonds are obtained in greater quantity from Brazil. 
The average product being about 15 pounds of dia- 
monds annually. 

482. Combustion of Carbon. — All of the forms of 
carbon are combustible. The combustion of charcoal 
in air is a familiar fact. Its combustion in oxygen has 

135 been already shown. Carbon burns as a 
spark; it is not changed into a gas until it 
unites with oxygen, it has, therefore, a greater 
illuminating power than other substances. 
This property will be more fully explained 
further on. The diamond and plumbago will 
also burn in a vial of oxygen gas, if first in- 
tensely heated. The product of their combustion, is 
precisely the same as that of charcoal. From the car- 
bonic acid, which is produced in the combustion, the 
carbon may be obtained in the form of lamp black. 
The nature of the diamond is thus conclusively estab- 
lished. 

483. Reduction of Ores by Charcoal. — The affin- 
inity of carbon for oxygen, at a high temperature, is 
very intense. It deprives most ores of their oxygen, 
and converts them into metals. An agent which thus 
produces metals from their compounds, is called a re- 
ducing agent, and the process is called reduction. 
Gaseous carbonic oxide has the same effect as carbon, 
because the affinity of its carbon for oxygen is only 
partially satisfied. In the process of reduction, these 

482. What is said of the combustion of carbon ? 483. How does char- 
coal reduce metals. 



CABBONIC ACID. 235 

reducing agents are themselves converted into carbonic 
acid, by the oxygen with which they combine. Hy- 
drogen gas, in consequence of its strong affinity for oxy- 
gen, is also a powerful reducing agent. The reducing 
power of carbon may be illustrated by sprinkling a lit- 
tle litharge on ignited charcoal, and blowing upon it at 
the same time, to maintain its heat. The litharge or 
oxide of lead will thus be partially converted into glob- 
ules of metal. 



Carbonic Acid. C0 2 

484. Description. — Carbonic acid is a, colorless gas, 
without much taste or smell, and about one and a half 
times as heavy as air. Other properties are illustrated 
in the experiments which follow. This gas is found in 
many mineral waters, and frequently escapes from fis- 
sures in the earth. It is a constituent of all limestones 
and shells, and forms ^- oli part of the atmosphere. It 
is exhaled from the lungs of all animals, and is a pro- 
duct of the combustion of coal and wood. 

485. Preparation. — Carbonic acid may be prepared 
by burning charcoal in oxygen gas, as directed in para- 
graph 352. Or it may be made by hanging a lighted 
candle, as long as it will burn, in a bottle filled with 
ordinary air. In this case, the carbon of the candle is 
converted into carbonic acid, by the oxygen of the air. 

484. What is carbonic acid? Where does it occur? 485. How is car- 
bonic acid prepared? 



236 



P R I N C I P L E i 



OF CHEMISTRY. 



But neither of these methods gives the unmixed gas, 
and that which follows is therefore to be preferred. 

486. Another Method. — Pour a tea-spoonful of mu- 
riatic acid into a large-mouthed half-pint vial, 
and then add bits of marble, chalk, or car- 
bonate of soda until effervescence ceases. 
The vial will then be filled with carbonic 
acid. 

For most of the experiments that follow, 
the second simple method of collection is 
sufficient, and the gas need not be trans- 
ferred to another vessel. When it is 
desired to obtain it separate from the 
materials from which it is produced, the 
apparatus represented in the figure may be employed. 

487. Carbonic Acid Prepared in Quantity. — - 

When larger 
quantities of this 
gas are required 
in a very pur 
state, the frs 
ments of mart 
are placed in a 
bottle, a, the 
dilute acid is 
pour ed in 
through the 





486. Give the second method of preparing it. 487. Describe another 
method of preparation. 



CARBONIC ACID. 237 

funnel, &, the gas escapes by the tube, c, and is collected 
in ajar placed over a tub of water as shown in the figure. 

488. Explanation. — Chalk and marble are both car- 
bonate of lime. As soon as they are dropped into mu- 
riatic acid, this stronger acid combines with the lime 
and retains it, setting the carbonic acid at liberty in the 
form of a gas. The gas as it accumulates, expels the 
air from the vial and completely fills it. It is obvious 
that in this method we do not make carbonic acid, but 
use that which nature has already made for us and im- 
prisoned in the marble. 

489. Carbonated Waters. — Water absorbs its own 
volume of carbonic acid and thereby acquires an acid 
taste. The so-called "soda water" or "mineral water," 
is prepared by confining water in a strong metallic ves- 
sel, and forcing into it gaseous carbonic acid, by means 
of a forcing-pump. The increased quantity which it 
is thus made to absorb is in precise proportion to the 
pressure employed. Neither of the above names give 
a correct notion of the nature of the 
effervescent drink referred to. It is 
simply carbonated water, to which soda 
is sometimes added. 

490. The absorption of carbonic acid 
by water may be shown, like that of 
chlorine, by the method illustrated in 
the figure. It may also be shown by pouring a gill of 
water into a half-pint vial of carbonic acid and then 

488. Explain the above process. 489. How are carbonated waters 
made ? 




238 



PRINCIPLES OF CHEMISTRY. 



shaking it. The palm of the hand being pressed closely 
upon the mouth of the vial, the flesh will be more or 
less drawn in, to take the place of the gas absorbed. 
The vial may be supported by this attachment. 

491. Effervescent Drinks. — Champagne, sparkling 
beer and mead, Congress water, and similar drinks, owe 
their effervescent qualities to this gas held in solution. 
On exposure to the air, the gas gradually escapes, and 
the liquids become insipid to the taste. The air enters 
and takes its place, expelling sixty or seventy times its 
own volume of gas. This effect may be hastened by 
striking, with the hollowed palm of the hand, upon the 
top of a glass partly filled with one of these liquids ; 
thereby compressing the air, and forcing it to enter 
rapidly. The carbonic acid immediately escapes with 
renewed and rapid effervescence. 

492. Flame Extinguished by Carbonic Acid. — 
Lower a lighted taper, candle, or splinter of wood into 

a vial of carbonic acid, pre- 
pared as above directed. 
The flame will be immedi- 
ately extinguished, as if it 
had been dipped in water. 

493. Or the same experi- 
ment may be performed by 
pouring the gas into a vial, 
at the bottom of which is a bit of 



140 





491. What is said of effervescing drinks ? 492. What effect has car- 
bonic acid on flame ? 493. Give another method of performing the ex- 
periment. 



CARBONIC ACID. 



239 



lighted candle. Nothing will be seen to flow from one 
vessel into the other, but the effect will be the same 
as before. 

494. Carbonic Acid heavier than Common Am, — 
Soap bubbles filled with common air float in carbonic 
acid gas. If we pour carbonic acid into a light jar 
poised upon a balance it causes that arm of the 
balance to de- 
scend because 
the carbonic 
acid is heavier 
than the air 
which it con- 
tained when 
the equilibri- 
um was adjusted. ' 

495. Carbonic Acid is Food for Plants. — Car- 
bonic acid is one of the principal elements of the food 
of plants. The leaves absorb it from the air, and the 
roots from the earth, and convert it into wood and 
fruit. The subject is further considered in the latter 
part of this work. 

496. It is Poison for Animals. — Water impreg- 
nated with carbonic acid is a healthful drink ; but the 
same gas when taken into the lungs, produces death. 
It operates negatively, by excluding the air, and also 
positively, as a poison. Being heavier than the air, 




494. How is carbonic acid shown to be heavier than air ? 495. Of what 
use to plants is carbonic acid ? 496. What is the effect of carbonic acid 
on animals ? 



240 PRINCIPLES OF CHEMISTRY. 

lakes of this gas sometimes collect in the bottom of 
caverns. There is a grotto of this kind in Italy, called 
the Grotto del Cane, or " dog's grotto." A man walking 
into it is safe, but his dog, whose head is below the 
surface of the gaseous lake, is immediately suffocated. 
Butterflies and other insects can be readily suffocated, 
without injury to their delicate organs or their beauti- 
ful colors, by placing them in a jar filled with carbonic 
acid. Baths of carbonic acid have recently been em- 
ployed, with advantage, in the treatment of rheuma- 
tism and other similar affections, and in cases of en- 
feebled vision. 

497. How Removed from Wells. — Carbonic acid 
often collects in the bottom of wells, and occasions 
danger, and sometimes death, to workmen employed in 
cleaning them. A candle previously lowered into the 
well will indicate the danger, if it exist. The flame 
will burn less brilliantly, or be entirely extinguished, 
if much of the gas is present. By repeatedly lowering 
pans of recently heated charcoal into the well, and 
drawing them up again, the gas will be absorbed and 
removed. The charcoal is. first heated, to increase its 
absorbing power. In this condition it absorbs thirty- 
five times its own bulk of gas. Dry slaked lime will 
also rapidly absorb carbonic acid. Exciting currents 
in the air of the well, as by throwing down buckets of 
water, or drawing water from the well causes the noxi- 
ous gas to rise into the atmosphere. The gas may even 

497. How is carbonic acid removed from wells ? 



CARBONIC ACID. 241 

be drawn up in buckets and poured away like so much 
water. 

498. Charcoal Fires in close Rooms. — Fatal acci- 
dents not unfrequently occur from inhaling the fumes 
of charcoal burned in close un ventilated rooms. These 
fumes consist of mingled carbonic acid and carbonic 
oxide. The latter gas will be hereafter described. 

499. Recovery from Poisoning by Carbonic Acid. 
— Persons who have become insensible by the action of 
carbonic acid may be resuscitated by dashing cold water 
upon them, rubbing the extremities and by the applica- 
tion of a warm bath if the body is cold. 

500. Solidification of Carbonic Acid. — One of the 
most interesting of all chemical experiments, is the 
solidification of carbonic acid. By combined cold and 
pressure, this transparent gas, which, under ordinary 
circumstances, is so thin that the hand, passed through 
it, does not recognize its presence, can be converted 
into a solid snow. This is done by bringing into a 
strong iron cylinder, connected by a tube with a second 
similar receptacle, the material for making more of the 
gas than there is room for in the two vessels. The 
cylinders being closed, and the gas produced by the 
agitation of the materials, it is evident that they must 
burst, or the gas must pack itself away in some more 
condensed form. The second vessel is surrounded by 
ice, and kept extremely cold, during the process. In 



498. How does burning charcoal cause fatal accidents ? 499. How may 
persons poisoned by carbonic acid be resuscitated ? 500. How may car- 
bonic acid be solidified 

li 



242 PRINCIPLES OF CHEMISTRY. 

this colder vessel the gas assumes a liquid form. Being 
removed in this condition, one portion of the liquid 
evaporates so rapidly as to freeze the rest. An explo- 
sive expansion of the liquid into gas would naturally 
be anticipated, but this does not occur. The materials 
used in the process are sulphuric acid and carbonate of 
soda. This experiment is attended with considerable 
danger and should only be performed in apparatus of 
great strength constructed for the purpose. 

501. Carbonic Oxide. — "When carbonic acid is passed 
through hot coals, it loses half of its oxygen and be- 
comes carbonic oxide. This takes place in coal fires. 
The coal in the lower part of the grate, where air is 
plenty, receives its full supply of oxygen and becomes 
carbonic acid. The hot coals above, where the supply 
of air is limited, take half of the oxygen from the car- 
bonic acid, and reduce it to this oxide, converting them- 
selves partially into carbonic oxide at the same time. 
The new gas passes on to the top of the fire, and there, 
where air is again abundant, it burns with a blue flame, 
and reconverts itself into carbonic acid. This gas is 
much more poisonous than carbonic acid, and is one 
source of the danger which arises from open fires in 
close rooms. One-two-hundredth of it makes the air, 
if inhaled for any considerable time, a fatal poison. 

502. Economy of Fuel. — A stove called the" Amer- 
ican Gas JSurner" furnishes several jets of heated air 
which enter the fire just above the burning coal, con- 

501. How is carbonic oxide formed ? 502. How may the most heat be 
obtained from a given amount of coal ? 



C A R BOXIC OXIDE. 



243 



verts all the carbonic oxide into carbonic acid, and for 
this reason furnishes more heat from the same fuel 
than if the carbonic oxide passed unburned into the 
chimney. 

503. Combustion of Carbonic Oxide. — For small 
experiments, the gas is best, prepared by covering a half 
tea-spoonful of oxalic acid" with 
oil of vitriol, and heating them to- 
gether in a test-tube. The gas, on 
being kindled at the mouth of the 
tube, burns with a beautiful blue 
flame. The experiment is rendered 
more striking by producing a jet, 
as represented in the figure. The 
gas thus obtained is really a mix- 
ture of carbonic oxide with car- 
bonic acid, but the admixture does not materially affect 
the experiment. 

504. Explanation. — Each molecule of oxalic acid 
contains carbon, oxygen and hydrogen, in the propor- 
tion to form one molecule each, of water, carbonic 
oxide and carbonic acid. Through the agency of sul- 
phuric acid this decomposition is effected. The water 
remains with the acid while the gases are evolved. 

505. It produces Metals from Oxides. — With the 
help of a high temperature, carbonic oxide takes oxy- 
gen from oxides, and converts them into metals. It 

503. How is carbonic oxide best prepared ? 504. Explain the forma- 
tion of carbonic oxide. 505. What is the effect on metallic oxides ? 




* This acid has the appearance of salt and is poisonous. 



244: PRINCIPLES OF CHEMISTRY. 

contains oxygen already, but its chemical appetite is 
only half satisfied with that element. It is this gas, 
produced in the fire, as before described, which con- 
verts iron ores into metal, in the smelting furnace. 
It is itself converted into carbonic acid at the same 
time. 

Silicon. 

Symbol, Si ; Equivalent, 14. 

506. Description. — Silicon is a dark gray substance, 
possessed of metallic luster, but classed with the metal- 
loids because it resembles them in its compounds. It 
is also called silicium. It is prepared from silica, by 
the method hereafter described for the production of 
calcium from lime. 

507. Silicic Acid or Silica. — Quartz 

144 

or rock crystal is nearly pure silica. It 
crystallizes in six sided prisms terminated 
by six sided pyramids. These crystals 
are sometimes called diamonds, but real 
diamonds are never found in this form. 
Transparent and colorless rock crystal is 
used for jewelry. In the form of Scotch 
pebbles it is used for spectacles. Sea-sand, flint, opal, 
jasper, agate, cornelian, amethyst and chalcedony, are 
other forms of the same substance, colored by the pres- 
ence of some metallic oxide. It also forms part of a 

506. What is silicon ? 507. What is silica 




silicon. 245 

very abundant class of rocks, called silicates, and prob- 
ably constitutes one-sixth of the mass of the earth. 
Silica occurs in many plants as in the cuticle of the 
scouring rush, in most of the grasses and grains, and in 
the bamboo, which belongs to the same family as the 
common grasses. Silica is an important ingredient in 
the manufacture of glass. 

508. Soluble Silica may be dissolved in water, by 
first fusing it with a large proportion of potash. On 
then adding acid, to neutralize the potash, the silica 
precipitates in the form of a jelly. Place a solution of 
silicata of potash in a cylindrical vessel formed of 
vegetable parchment (See Part IV); place this cylinder 
in a vessel of water and add to the silicate muriatic 
acid sufficient to neutralize the potash ; the muriate of 
potassa will all pass through the parchment into the 
outer vessel while the silica will remain in a state of 
solution. By keeping the apparatus perfectly quiet a 
solution containing nearly thirty per cent, of silica may 
be obtained. On agitating the solution it will at once 
assume the gelatinous form. By this circuitous process 
the most gritty sand is converted into a soft jelly. A 
singular application of this rock-jelly, in the adultera- 
tion of butter, has recently been detected in England. 
Dissolved silica also occurs in nature, and hardens into 
agates, onyx, and other precious stones. 

509. Petrifactions. — As wood wastes away in cer- 



508. How can silica be made soluble ? 509. What is the cause of petri- 
faction ? 



2i6 PRINCIPLES OF OHEMISTEY. 

tain silicious waters, the particles of silica take, one by 
one, the place of the departing atoms, and thus copy 
the wood in stone. Such copies are called petrifactions. 

Boron. 

Symbol, B; Equivalent, 10.9; 

510. Description. — Boron is a brown powder, never 
seen except in the chemist's laboratory, and of no prac- 
tical value. It occurs in nature, combined with other 
elements, as borax and boracic acid. 

511. Boracic Acid. — This acid is commonly seen in 
the form of white pearly scales, which have a greasy 
feel. Dissolved in alcohol it burns with a green flame. 
It exhales with volcanic vapors which issue from the 
earth in Tuscany. These vapors are condensed in 
water, and the solid acid is obtained by evaporating the 
solution. It is bitter, rather than sour, to the taste, 
but is called an acid because it forms salts. 

Boracic acid communicates to its compounds the 
property of ready fusibility, and on this property its 
value chiefly depends. Many of the borates are used 
as fluxes, which are applied as glazing for porcelain and 
in the melting of gold and silver. If steam at a high 
temperature is transmitted over boracic acid, the acid 
is volatilized in considerable quantities. It is in this 
way raised to the surface of the earth in Tuscany by 
the jets of steam which issue from the strata below. 

510. What is boron ? 511. How is boracic acid formed? 



BORON. 247 

These vapors are condensed by artificial pools of water, 
a, figure 145, into which they are received. The solu- 
tion is still further condensed in other shallow basins, 5, 




and afterwards evaporated in shallow pans, P P, by the 
heat of jets of steam issuing from the earth through 
flues, y, under the evaporating pans. About two thou- 
sand tons of the crude acid are thus procured in Tus- 
cany. It is also obtained in Thibet as a biborate of 
soda called tincal. Combined with lime and magnesia 
boracic acid is obtained in South America. 



Hydrogen. 

Symbol, H. Equivalent 1. Specific Gravity, 0.0692 (Air being =1). 

512. Description and Occurrence. — Hydrogen is a 
colorless gas, about one-fifteenth as heavy as the air. 
It is of such extreme tenuity, that it may be blown 
through gold leaf and kindled on the opposite side. 
One-ninth part of the ocean, and the same proportion 

512. What is hydrogen ? W r here does it occur ? 



248 



PRINCIPLES OF CHEMISTRY. 




of all water in existence, is hydrogen gas. It enters, 
also, largely into the composition of all animal and 
vegetable matter, and forms the basis of most liquids. 
513. Preparation. — Introduce a few bits of iron or 
zinc into a vial one-third filled 
with water. Add a tea-spoonfull 
or more of common sulphuric 
acid, and attach to the vial a 
bent tube or a clay pipe, as re- 
presented in the figure. The 
evolution of the gas immediately 
commences. The first portions, which contain an ad- 
mixture of air, are allowed to escape ; the pipe-stem is 

then brought under the 
mouth of the vial, and 
the gas collected. 45, 

"When a considerable 
quantity of hydrogen 
is required, the appa- 
ratus shown, in figure 
147, is more conven- 
ient, and the gas is col- 
lected in jars over wa- 
ter. If a considerable 



147 




513. Describe the methods of preparing hydrogen. 



* When a taper can be applied at the mouth of the pipe-stem without explosion, 
it may be certainly known that an unmixed gas is in process of evolution. A cloth 
should be thrown over the vial and this test made before commencing the collection. 
The connection of the apparatus in the above experiment is made with a paper stop- 
per, formed on a bit of pipe-stem or glass tube. 



HYDROGEN. 249 

quantity of acid and zinc is placed in the jar, a, the evo- 
lution of gas becomes so rapid that the dilute acid is car- 
ried over with the gas. The tube, 5, extending below 
the fluid in a, renders it easy to add the acid in small 
quantities, so as to keep up a moderate and continuous 
evolution of hydrogen. A wash bottle, d, contains 
potash dissolved in alcohol to absorb acid vapors, sul- 
phuretted hydrogen and carbonic acid, which are fre- 
quently produced by impurities in the materials em- 
ployed for preparing hydrogen. One ounce of zinc is 
sufficient to liberate 2| gallons of hydrogen. 

514. Explanation. — Water is composed of oxygen 
and hydrogen gases. Each would be a gas, but for the 
other, which holds it in the liquid form. In the above 
process for preparing hydrogen, the zinc is, as it were, 
the ransom paid for its liberation. The oxygen com- 
bines with the zinc, and the hydrogen escapes. 

515. Pure water will not suffice in the process. It 
must contain acid, to unite with the oxide of zinc, as 
fast as formed. The presence of an acid, for which the 
oxide has great affinity, seems to stimulate its forma- 
tion. It may, indeed, be regarded as a general law, 
that the presence of acids promotes the formation of 
oxides, and vice versa. 

516. Another Method. — Hydrogen may also be 
made by passing steam through a heated gun-barrel 
containing bits of iron. Bundles of knitting needles 
are commonly employed for the purpose. The steam 

514. Explain the formation of hydrogen ? 515. What purpose is served 
by the acid ? 516. Give another method of preparing it. 



250 PRINCIPLES OF CHEMISTRY. 

leaves its oxygen, combines with the iron, and escapes 
as hydrogen gas. 

Note. — Although red hot iron thus decomposes vapor of water, 
forming oxide of iron, yet if hydrogen is passed over red hot oxide 
of iron, the hydrogen takes the oxygen from the iron and forms 
water, leaving the iron in the metallic state. The affinity of iron 
and hydrogen for oxygen is so nearly balanced that whether the 
iron or hydrogen shall hold the oxygen depends upon the relative 
temperatures and the abundance in which one or the other sub- 
stance is present. 

517. Water Gas. — When vapor of water is passed 
over charcoal heated to redness, the water is decom- 
posed, and the hydrogen is set free. The oxygen of 
the water unites with the carbon to form carbonic acid, 
C0 2 , and a small quantity of carbonic oxide, CO, to- 
gether with a little light carburetted hydrogen, C 2 H. 
The mixed gases are then passed through milk of lime, 
to remove the carbonic acid, and the remaining gas, 
which is mostly hydrogen, is employed for heating and 
illuminating purposes under the name of water gas. 
A jet of burning hydrogen gives but little light, and 
the same is true of the water gas ; but if the flame is 
enveloped with a cage of platinum wire a brilliant light 
is produced. If the water gas is passed through rock 
oil a part of the oil is carried in a state of vapor with 
the gas and greatly increases the brilliancy of the light. 
But the volatile oil carried over with the gas is soon 
deposited and clogs the gas pipes. 

518. Combustion of Hydrogen. — Bring a dry cold 

517. How is the material called water gas produced? 518. What is 
produced by the combustion of hydrogen ? 



HYDROGEN. 251 

tumbler over a burning jet of hydrogen. The vessel 
will soon become moistened on the interior. The 
water thus produced, is a result of the combination of 
hydrogen with oxygen of the air. But for the cold 
surface, with which it is brought into contact, it would 
have escaped into the air as vapor. 

148 



In the experiment shown in the figure, the hydrogen 
is first passed through a tube filled with chloride of cal- 
cium to absorb any traces of moisture which might 
pass over from the bottle in which the hydrogen is 
generated. The water formed is seen trickling down 
the sides of the bell glass into the dish placed to collect it. 

The composition of water ^. 

was shown in Part I., (§ 268,) 
by Galvanic decomposition. It 
is here demonstrated by com- 
bining its elements and thus 
reproducing it. "Water is also 
formed in the combustion of 
any substance containing hy- 
drogen as one of its constituents. The above experiment 
may therefore be made with a lighted lamp or candle. 




252 



PRINCIPLES OF CHEMISTRY. 




as well as with the jet of pure hydrogen. This experi- 
ment shows that the candle contains hydrogen. 

15 °- 519. Philosopher's Lamp. — If a tube 

is inserted into the mouth of a vial or 
flask containing the materials for pro- 
ducing hydrogen, the gas as it issues 
may be ignited, when it will burn with a 
delicate and almost invisible flame. This 
apparatus, which is shown in the figure, is 
called the philosopher's lamp. The gas 
should always be allowed to issue several 
minutes before it is ignited, so that all the 
air in the bottle may pass oft"; otherwise 
an unpleasant explosion might occur. 

520. Explosion of mixed Oxygen and Hydrogen. 
-Allow oxygen to flow into an inverted vial, as directed 

in paragraph 343, until it is one-third full. 
Fill it up with hydrogen, collected as shown in 
Sec. 513. Cork the vial under water. It is 
now filled with an explosive mixture, which 
may be fired by the application of a taper. 
To secure against accident, the precaution 

should invariably be observed of winding the vial with 

a towel, before the discharge. 

521. Explanation. — The explosion results from the 
fact that all of the hydrogen in the vial burns at once, 
causing great heat, and sudden expansion of vapor. 
The combustion is thus simultaneous, because oxygen, 



519. Describe the philosopher's lamp. 520. How is an explosive mixture 
prepared ? 521. Why does this mixture explode ? 



HYDROGEN. 253 

the supporter of combustion, is present at every point. 
When on the other hand a jet of hydrogen is kindled, 
no explosion occurs, because the combination is gradual. 
Combustible hydrogen meets with oxygen in this case, 
only on the surface of the jet. 

522. The Hydrogen Gun. — The experiment for the 
explosion of mixed hydrogen and oxygen gases, may 
be made in a strong tin tube, provided with a vent 
near the closed end. Such a tube, about an inch in 
diameter, and eight inches in length, is called the hy- 
drogen gun. In loading it, the vent is stopped with 
wax, the tube filled with water, and the gases, previ- 
ously mixed in the right proportion, poured upward 
into it, as indicated in the figure. 
The gun, being thus loaded, is tightly 
corked under water, and afterward 
fired at the vent. The explosion is 
sufficient to expel the cork with vio- 
lence, accompanied by a loud report. 
The vial from which the tube is loaded 
must not be too large, or it will not be 
practicable to turn it and pour upward, as desired. 
This difficulty may also be obviated, by the substitution 
of a water-pail, for the bowl represented in the figure. 

523. Charge of Air and Hydrogen. — As air con- 
tains uncombined oxygen, a mixture of air and hydro- 
gen also forms an explosive mixture. But, as air is 
only one-fifth oxygen, five times as much of it must be 

522. Describe the hydrogen gun, and the method of charging it. 523. 
Describe another explosive mixture. 




254 



PRINCIPLES OF CHEMISTRY. 



used ; in other words, five parts of air are required, for 
every two parts of hydrogen. To make the mixture, 
hydrogen may be led, as before, into an inverted vial a 
little more than two-thirds full of air. The exact pro- 
portion is not essential in this, or any similar case of 
explosive mixture. 

524. A Simpler Method. — A simpler method of 
loading the gun, or charging the vial with the explosive 
mixture, is to invert it over a jet of hydrogen, as repre- 

sented in the figure. The pipe-stem, or tube, 
which conveys the gas, is previously wound with 
paper, until it occupies about two-thirds of the 
inner space of the gun. Escaping hydrogen fills 
the remainder. On withdrawing the tube, air 
enters to take its place, and the gun is thus 
charged with mixed air and hydrogen, in the 
right proportions. It is then corked and fired. 
This experiment may also be made with a test- 
tube, discharging it at the mouth. Explosions 
with mixed air and hydrogen, are, of course, less vio- 
lent than when pure oxygen is used instead of the 
diluted oxygen of the air. 

525. Production of Musical Tones. — When a jet 
of hydrogen escaping from a small aperture is set on 
fire it burns with a tranquil and almost invisible flame, 
as in the case of the philosopher's lamp ; but if an open 
glass tube is held over the jet so as to form a chimney, 



524. Give a simpler method of loading the gun. 525. How are musical 
tones produced by burning hydrogen ? 



HYDROGEN. 



255 



154 



155 



the hydrogen will burn with a flickering flame. A 
succession of little explosions is produced which follow 
sach other so rapidly as to produce a continuous sound 
or musical note. The longer and narrower the tube 
the more acute will be the note produced. By using a 
series of tubes of proper diameters and lengths all the 
notes in the musical scale may be produced. 

526. Hydrogen will not support Combustion. — 
Flame is extinguished in hydrogen, as it would be in 

water. Re-charge the gas 

bottle, if necessary, and hang 

a second large-mouthed vial 

above it, as represented in the 

figure. After a few minutes, 

it may be presumed that the 

upper vial is filled with hydro- 
gen. Apply a lighted match 

to its mouth, and the gas 
will inflame and continue to burn with a faint light. 
Introduce a taper into a jar of this gas as represented 
in figure 155. It will be kindled at the mouth of the 
jar, and again extinguished above. The match is ex- 
tinguished, figure 154, because, a little above the mouth 
of the vial, there is no oxygen to support the combus- 
tion of the carbon and hydrogen of which it is composed. 

527. Hydrogen made by the Metal Sodium. — 
Another very beautiful but more expensive method of 
making hydrogen gas, is as follows. Fasten a piece of 





526. Does hydrogen support combustion ? 527. Describe the prepara- 
tion of hydrogen by sodium. 




256 PRINCIPLES OF CHEMISTRY. 

metallic sodium, of the size of a pepper-corn, upon 

the end of a wire and thrust it suddenly under the 
end of a test-tube filled with water, 
and held very near the surface, as 
represented in the figure. The 
metal melts as soon as it touches 
the water, and rises to the top of the 
tube. Hydrogen is immediately 

formed, and displaces the water, filling the tube rapidly 

wdth the liberated gas. 

528. Explanation. — Sufficient heat is evolved by the 
action of sodium on water to fuse it at once. The 
metal is lighter than water, and therefore rises to the 
top of the tube. At this point the chemical process 
begins. Sodium has the most intense affinity for oxy- 
gen, and therefore combines with this element of the 
water, setting its hydrogen at liberty. JSTo acid is re- 
quired as in the case of zinc. Metallic potassium may 
also be used in this experiment. To avoid its ignition 
by contact with the water, it is to be wrapped in paper, 
and the twisted end of the wrapper used as a holder, 
with which to thrust it under the mouth of the tube. 

Water. 

Symbol, HO; Equivalent, 9; Specific Gravity, 1. 

529. Composition. — Many important properties of 
water have already been illustrated in the chapter on 
Vaporization. Others w^ill be mentioned below. It is 

528. Explain the process. 529. Of what is water composed ? 



WATER. 257 

composed of oxygen and hydrogen, as has already been 
proved both by analysis and synthesis. These gases 
are condensed in combination to about 20V o °f their 
original volume. It remains to show how the exact 
proportion in which they enter into the composition of 
water is ascertained. 

530. First Method of Proof. — One method is to 
decompose water by the Galvanic process, and collect 
and weigh the erases obtained. 

° ° ^ 157 

Two jars or tubes are filled 
with water and inverted in 
the pneumatic cistern. Un- 
der the tubes are metallic 
plates connected by wires 
with the cups A and B which 
are filled with mercury. The 
positive pole of a Galvanic 
battery is placed in A and the negative pole in B. 
When the connection is formed the water is decomposed 
the oxygen collects in O and the hydrogen in H. The 
oxygen is found to weigh eight times as much as the 
hydrogen. Water is thus shown to be composed of 
eight parts of oxygen, by weight, to one part of hydro- 
gen. In other words, nine pounds of water contain 
eight pounds of oxygen and one pound of hydrogen. 

531. Secoistd Method. — Another method is to meas- 
ure the gases obtained by the same method of decom- 
position. Two measures of hydrogen are thus obtained 

530. Describe the method by Galvanic decomposition. 531. Show how 
composition by weight may be calculated from measure. 




258 PRINCIPLES OF CHEMISTRY. 

for every single measure of oxygen. The chemist then 
proceeds to calculate the relative weight. Knowing 
beforehand that hydrogen is the lighter gas, weighing 
but one-sixteenth as much as the same quantity of oxy- 
gen, he infers that the double volume obtained in the 
above experiment, weighs but one-eighth as much as 
the oxygen obtained in the same decomposition. The 
result of this indirect process is the same as that stated 
at the conclusion of the last paragraph. 

532. Third Method. — A third method consists in 
reproduction of water from mixed hydrogen and oxy- 
gen, observing at the same time the quantities in which 
they combine. This may be readily effected in a test- 
tube. The gases being introduced into the tube in 

about the right proportion, and in small 
~ quantity, its extremity is then intensely 
^Jwh heated. A slight explosion and combi- 
^^^S^i nation of the gases is the result, and the 
Mi^jB^^te water rises to take their place, mingling 
^^~ with the small quantity of water pro- 
duced in the experiment. Any excess of either gas 
remains uncombined. Whether this surplus is oxygen 
or hydrogen, may be readily proved by methods previ- 
ously given. This excess being substracted from the 
quantity of the same gas originally used, shows the 
proportion in which the combination has occurred. 

533. The explosion may be avoided, and a gradual 
combination of the gases effected, by evaporating a few 



532. Describe the third method. 533. How may the explosion be 
avoided ? 



.... Vatee. 259 

drops of platinum solution in the test-tube, and igniting 
the residue previous to the commencement of the above 
experiment. A ball of fine iron wire is then crowded 
into the end of the tube. The mixture of gases being 
finally introduced, the least touch of flame upon the 
end of the tube is sufficient to effect a gradual combi- 
nation. For an explanation of the agency of platinum 
in the above experiment, the student is referred to the 
chapter on metals. The iron wire serves to prevent 
ignition, and consequent explosion, by appropriating 
part of the heat produced by the combination of the 
gases. The form of the experiment last described, is 
the only one that can be recommended to the student. 
With the security against explosion which it affords, a 
test-tube filled with the mixed gases may be submitted 
to experiment. Where very accurate results are 
sought, the process must be conducted in a carefully 
graduated tube. By employing mercury instead of 
water, the water produced in the experiment may be 
seen. 

534. Fourth Method. — Still another method is illus- 
trated in the figure. It consists essentially, in the pro- 
duction of water from its elements as before ; furnishing, 
at the same time, the means of ascertaining the propor- 
tional weight of the gases which have taken part in 
its formation. By means of an aspirator, a current of 
perfectly pure and dry hydrogen gas is made to pass 
over a weighed portion of oxide of copper at a red 
heat ; the hydrogen, at a high temperature, takes away 

534. Give the method by oxide of copper 




260 PRINCIPLES OF CIlSyflffiTRY. 

the oxygen from the oxide of copper, and, uniting with 
it, forms water, which is absorbed by a tube contain- 
ing fragments of pumice stone saturated with oil of vit- 
riol. The aspirator* shown 
in the figure, affords the 
means of drawing the gas 
through the tubes, as in the 
analysis of air (§ 436). Both 
tubes are afterward weighed, and their gain or loss de- 
termined by comparison with their weight before the 
commencement of the process. 

535. The loss of weight in the one tube, expresses the 
weight of the oxygen which it has furnished for the for- 
mation of water ; the gain in the second tube gives the 
weight of the water thus formed. The difference of 
the two, gives the weight of the hydrogen which has 
been appropriated in its passage, and now makes part 
of the newly formed water. For every nine grains of 
water thus produced, it is found that eight grains of 
oxygen, and one of hydrogen have been consumed. Its 
precise composition is thus demonstrated by another 
and quite distinct process. 

536. Solution. — Water is a very general solvent. 
The disappearance of salt or sugar, in water, is an ex- 
ample, f Transparency is essential to a solution. 

535. How are the results calculated ? 536. Wliat is said of solution ? 



* A vessel employed, as in the present instance, to produce a current of air or gas, 
is called an aspirator. 

t Water also dissolves many gases. The ammonia of the shops is prepared by 
passing gaseous ammonia into water. 



WATER. 261 

Where the particles of a solid are distributed through- 
out a liquid, as when chalk is stirred with water, it is 
said to be diffused, instead of dissolved. The solvent 
action of water plays a most important part in nature, 
as will be seen in another chapter of this work. The 
subjects of solution and precipitation, are more fully 
considered in the chapter on salts. 

537. Precipitation. — Where a substance which has 
been dissolved is re-converted into a solid form, it is 
said to be precipitated. Thus, when air from 
the lungs is blown through a pipe-stem into 
lime-water, the lime combines with the car- 
bonic acid from the lungs, and falls to the bot- 
tom of the vessel, in the form of solid par- 
ticles of chalk. The solid thus produced is 
called a precipitate. 

The addition of a few grains of alum to a barrel 
of water coagulates organic matter which it often 
contains, and causes it to settle to the bot- 
tom. River water is . often purified in this 
manner. 

538. Filtration. — Filtration is the separa- 
tion of a precipitate from the liquid in which 
it is contained. This is effected by throwing 
the mixture into a paper cone, which retains 
the solid, while the liquid passes through its pores. 
Such a filter is prepared by folding unsized paper into 
the shape of a quadrant, which is then opened, so as to 

537. What is precipitation? 538. What is nitration, and how is it 
effected ? 





262 PRINCIPLES OF CHEMISTRY. 

form a cone, commonly supported in a glass funnel. It 
is possible, in small experiments to dispense with the 
funnel, as is done in the figure, and even to use ordi- 
nary newspaper in the place of that especially prepared 
for the purpose. 

Matter actually dissolved in water is not affected by 
filtration. No repetition of filtration would withdraw 
the salt from seawater and make it fresh. Hence the 
impregnation of peaty matter, which river water gene- 
rally contains, and to the greatest extent in summer 
when the water is concentrated by evaporation, is not 
removed by filtering. 

539. Purity of Water. — In nature water is never 
found entirely pure. Rain-water contains air and 
other gases in a state of solution, as well as considerable 
dust collected from the atmosphere. So also various 
mineral substances which are carried into the air in a 
state of vapor, are found condensed and dissolved in 
rain water. Biver-water contains considerable vege- 
table matter which it has dissolved as it has flowed 
over the hills and fields from whence it has been col- 
lected. 

The presence of vegetable and animal matter in 
river-water often renders it injurious to health until it 
has been kept in tanks or reservoirs and undergone a 
species of fermentation by which organic matter is 
reduced to the inorganic condition and separated by 
precipitation. 

Spring-water in addition to air and carbonic acid in 

539. What is said of the purity of natural waters ? 



WATEE. 263 

a state of solution* always contains more or less min- 
eral matter dissolved in it. "When spring-water con- 
tains so much mineral matter as to give it a decided 
taste the spring from which it comes is called a mineral 
spring. 

540. Hakd and Soft Water. — Water which contains 
lime or magnesia in solution in any appreciable quan- 
tity is called hard water. The familiar method of 
determining the presence of these substances is by the 
action of the water upon soap which is curdled by both 
lime and magnesia. Water which curdles soap is called 
hard and that which has no such action is called soft 
water. Soft water has a greater solvent power over 
most substances than hard water, it is therefore more 
suitable for washing and other domestic purposes than 
hard water. Soft water acts upon lead pipes dissolving 
the oxide of lead formed upon its surface, which imparts 
poisonous properties to the water. Hard water is less 
injured by contact with lead. All extracts and soups 
are best prepared with soft water, while vegetables 
boiled in hard water, or water to which salt has been 
added, retain their flavor better than if boiled in soft 
water. Tet beans and peas which require to be made 

540. WTien is water said to be hard ? and when soft ? 



* Water at 32° F. dissolves 1.8 its own volume of carbonic acid, 0.04 of oxygen 
and 0.02 of nitrogen, while at 59 3 F. it dissolves one volume of carbonic acid, 0.03 
of oxygen and 0.015 of nitrogen. It will be seen that this is a much greater pro- 
portion of oxygen and carbonic acid and less nitrogen than is found in common air. 
From the gases thus dissolved fishes obtain oxygen and plants carbonic acid. At an 
altitude of 6 or 8000 feet water contains only one-third the usual amount of air. 
Hence fishes cannot live in Alpioe lakes as the water does not contain sufficient air 
to sustain their respiration. 



264 PRINCIPLES OF CHEMISTRY. 

soft by boiling should be cooked in soft water, or water 
to which a little soda has been added. 
t63 541. Crystallization. — Dissolve half a pound 

of alum in a pint of boiling water, and hang a 
cotton cord in the vial. As the water cools, 
crystals will form on the thread. Bonnet wire 
may be bent into the shape of baskets, miniature 
ships, &c, and covered by this means, with a 
beautiful crystallization. 

542. Explanation. — Hot water has for most 
substances greater solvent power than cold water. 
In the case of alum, for example, water slightly warmed 
will dissolve twice as much as cold water. It follows, 
that as the hot water becomes cold, part of the alum 
must become solid again. In so doing, the particles, 
in obedience to their mutual attraction, arrange them- 
selves in crystals, as described in Chapter III. 

543. Snow Crystals. — Snow flakes are always either 
grouped or single crystals, and their form may often be 

distinctly seen with the 

II § / *i& naked eye. They are best 

l_} ^K lm0£ iplf observed by catching them 

upon a hat, or other dark 
object, and inspecting them in the open air. 

544. Chemical Combinations. — Water unites with 
both bases and acids, to form hydrates. Thus, with 
lime, it forms hydrate of lime ; with sulphuric acid, 



541. How may crystals of alum be obtained ? 542. Explain the pro- 
cess. 543. What is said of snow crystals ? 544. What is said of the 
combinations of water ? 



WATER. 265 

hydrated sulphuric acid. Most of the oxygen acids, in 
the form in which we employ them, contain water in a 
state of combination, and are therefore hydrated acids. 
They may also be regarded as salts, of which oxide of 
hydrogen or water is the base. 

545. Relations to Life. — Water forms, by far, the 
greater part of all animal and vegetable matter, as will 
be more fully seen in the portion of this work which 
treats of organic chemistry. To water the leaf of the 
vegetable and the muscle of the animal, owe, in a great 
degree, their pliancy and freedom of motion. In view 
of these and other relations to life, the negative prop- 
erties of water are not the least important. Had it 
taste or odor, however exquisite, we should soon weary 
of them. And but for its mild and neutral character, 
it would irritate the delicate nerves and fibers which it 
bathes. 

"Water exists in organized bodies in two different 
states. In one it may be considered as an essential 
part of the structure which cannot be removed without 
destroying the compound body of which it forms a part. 
In the other condition it is merely diffused through the 
structure and may be removed by drying. 

Water is the medium in which the food both of 
plants and animals is diffused and circulated through 
their systems and from which the nutriment is deposited 
in the growing parts. 

546. At very high temperatures the vapor of water 

545. What is said of water in its relations to life ? 546. What is the 
effect of water at high temperatures ? 



266 PRINCIPLES OF CHEMISTRY. 

decomposes many minerals, and expels strong acids 
from their compounds. Under the stimulating influ- 
ence of heat, this neutral liquid becomes a chemical 
agent of extreme energy. Such decompositions as are 
here referred to, are without doubt, constantly going on 
beneath the surface of the earth. 

547. Fog — Vesicular Yapor. — Fog is supposed to 
consist of water in the form of hollow vesicles filled 
with air. "When the vapor of water is mixed with air 
it is believed to have a tendency to condense in vesi- 
cles which (like soap bubbles) contain air ; forming in 
this condition visible vapor, as fog, mist, or masses of 
clouds which float in the atmosphere from the lightness 
of the vesicles. The air within is rendered lighter than 
the surrounding air by the condensation of the watery 
envelope which emits the heat previously latent when 
the water existed in the form of steam. Vesicles of 
this kind may be observed by a lens of one inch focal 
length over the dark surface of hot tea or coffee to- 
gether with an occasional solid drop which contrasts 
with them. Vesicles of mist vary from 4^ th to 
YaV th of an inch in diameter, and it has been com- 
puted that it would require 200,000,000 fog globules to 
make a drop of rain one-tenth of an inch in diameter. 
"Watery vesicles of which the clouds are composed are 
said to be condensed by collision into solid drops and 
fall as rain, but in some states of the atmosphere these 
drops are again evaporated as fast as they are formed. 
It is proper to add, that Prof. J. Forbes and several 

547. What is the condition of water in fog, or mist? 



WATER. 267 

other eminent meteorologists disbelieve entirely the 
existence of vesicles in watery vapor. 

Compounds of Hydrogen, with Chlorine, Bromine, 
Iodine, Fluorine, and Sulphur. 

548. Under this head are to be described a new series 
of acids, distinguished from all which have hitherto 
been mentioned by the absence of oxygen. The mole- 
cules of each, like those of water, are composed of 
single atoms of their constituents. 

They are all gaseous, and are sometimes called hy- 
dracids, from the hydrogen which enters into their 
composition. Their salts are described in Chap. III. 

Hydrochloric Acid. 

Symbol, HC1 ; Equivalent, 37. 

549. Description. — Hydrochloric acid is a colorless 
gas, fuming by contact with the air. It sometimes 
issues from volcanoes, but is, for the most part, an 
artificial product. Its solution in water is known as 
muriatic acid. 

550. Preparation. — Gaseous hydrochloric acid may 
be produced, like water, by the direct combination of its 
elements. For this purpose, equal volumes of the two 
gases are mixed by candle-light or in carefully covered 
bottles, and then exDosed to the direct rays of the sun. 
The action of the light is so intense, that on throwing 

548. What are hydracids ? 549. What is hydrochloric acid ? What is 
said of its occurrence ? 550. Describe its preparation. 



268 



PRINCIPLES OF CHEMISTRY. 



a bottle thus filled from shadow into sunlight, it imme- 
diately explodes. The explosion is a consequence of 
the energetic union of the two gases, under the influ- 
ence of the chemical rays of the sun. The acid pro- 
duced is at once dissipated in the air. Great caution 
should be used in this experiment, for even the diffused 
light of day has been known, in some instances, to 
occasion explosion. 

551. Another Method. — Hydrochloric acid may 
also be made from common salt, which furnishes the 
chlorine, and ordinary hydrated sulphuric acid, which 
furnishes the hydrogen. A tea-spoonful of common 
salt is introduced into a test-tube with about the same 
bulk of water. Half as much acid is added, the mix- 
ture then gently heated, and the acid gas led into water, 
as shown in figure 164. Water absorbs, at ordinary 

161 165 




temperatures, 480 times its own 
volume of the gas. Figure 165 
shows a convenient form of 
apparatus for performing this 




551. Describe another mode of preparing it ? 



HYDROCHLORIC ACID 26& 

experiment on a larger scale. There is no occasion, for 
tlie purpose of experiment, to carry on the process till it 
is thus saturated. A few minutes will suffice to make 
an acid strong enough to dissolve zinc. 

552. Explanation. — Hydrated sulphuric acid has 
always a strong tendency to form metallic salts. In 
this case it takes the metal, sodium, from the common 
salt, and thereby converts itself into sulphate of soda. 
At the same time it gives back hydrogen to the salt, in 
place of its lost sodium, converting it, by the exchange, 
into hydrochloric acid. The process just described, is 
the one always employed in the manufacture of hy- 
drochloric acid. 

553. Action of Hydrochloric Acid on Metals. — 
Hydrochloric acid dissolves tin and all of the metals 
which precede it in the chapter upon metals. For tin, 
a hot and concentrated acid must be employed. 

554. The solution depends on the fact that the metals 
take chlorine from the hydrochloric acid, thereby con- 
verting themselves into soluble chlorides. The hydro- 
gen then assumes the gaseous form, and escapes with 
lively effervescence. An experiment may be best made 
with zinc, covered with a little dilute acid. 

555. Aqua Regia. — On mixing nitric acid with half 
of its bulk of strong hydrochloric acid, aqua regia is 
produced; so called, from its regal power over the 
noble metals. "When nitric and muriatic acids are 



552. Explain the process. 553. What metals does hydrochloric acid 
dissolve ? 554. On what does the solution depend ? 555. What is aqua 
regia ? 



270 PRINCIPLES OF CHEMISTRY. 

mixed they mutually decompose each other. The 
quantities necessary to render the decomposition com- 
plete are one equivalent of each. The quantities re- 
quired will therefore depend upon the relative strength 
of each acid employed. Acids of the strength usually 
sold require one measure of nitric to two measures of 
muriatic acid. When the stronger acids are mixed a 
considerable portion of chlorine escapes and is lost. 
Gold and platinum, which are not affected by either 
acid alone, dissolve readily in aquia regia. The sol- 
vent power of aqua regia depends, as before explained, 
on the nascent chlorine which it supplies. 

556. Hydrobromic and Hydriodic Acids. — These 
acids are of interest to the chemist only. They resem- 
ble hydrochloric acid, in being colorless gases, strongly 
acid, soluble in water, and capable of dissolving many 
metals. 



Hydrofluoric Acid. 

Symbol, HF; Equivalent, 39. 

557. Description. — Hydrofluoric acid is a colorless, 
corrosive gas, acting on glass and many minerals which 
other acids do not affect. It condenses into a liquid at 
the freezing point of water. It is not known to occur 
ready formed in nature. 

558. Preparation. — Hydrofluoric acid is made from 

556. What is said of hydrobromic and hydriodic acids ? 557. What is 
hydrofluoric acid ? 558. How is hydrofluoric acid prepared ? 



HYDROFLUORIC ACID. 271 

a mineral called fluor spar, by the same means em- 
ployed to make hydrochloric acid. On account of its 
corrosive action on glass, vessels of lead or platinum are 
employed in the process. This gas is so poisonous, 
when inhaled, and its solution so corrosive to the skin, 
that its preparation, in any considerable quantity, should 
be left to the experienced chemist. 

559. Explanation. — In the above process, the fluor 
spar, which is a fluoride of calcium, furnishes the fluo- 
rine, and hydrated sulphuric acid, the hydrogen. The 
remaining constituents unite to form sulphate of lime, 
which remains in solution. 

560. Etching on Glass. — It has already been stated 
that hydrofluoric acid attacks glass and many minerals. 
By covering with wax, they may be protected against 
the corrosion. Advantage is taken of 160 
these two facts in etching upon glass. 
The surface is first slightly warmed 
and rubbed with beeswax, and then 
warmed again, to produce an even coating. Figures or 
letters are then drawn upon the glass, through the wax, 
with a pen-knife or other pointed instrument. The 
plate being now exposed for a few minutes to the fumes 
of hydrofluoric acid, and the wax subsequently removed, 
is found to be deeply etched. Fumes of hydrofluoric 
acid for the purpose, are best obtained by placing a 
half tea-spoonful of pulverized fluor spar in a warm 
tea-cup, and covering the powder with oil of vitriol. 

559. Explain the process ? 560. Give the process for etching upon glass. 




272 PRINCIPLES OF CHEMISTRY. 

A little ether or potash will be found of use in remov- 
ing the last portions of wax from the plate. 

561. Explanation. — As oxygen combines with car- 
bon to form carbonic acid, so the hydrofluoric acid eats 
out the silicon of the glass, where it is exposed, and 
passes off with it, in the form of a new and more com- 
plex gas. A solution of the gas may be prepared by 
the process employed for hydrochloric acid. Bottles of 
vulcanized India rubber or gutta percha may be used 
in keeping the solution. 



Hydrosulphuric Acid. 

Symbol, HS ; Equivalent, 1 7. 

562. Description. — Hydrosulphuric acid is a color- 
less gas, also known as sulphuretted hydrogen. It has 
a putrid odor and feeble acid properties. Like the rest 
of the series, it is soluble in water. It occurs in many 
natural waters, called sulphur springs. It is one of the 
products of the decomposition of animal matter, and 
the source of much of the disgusting odor which they 
emit during putrefaction. 

563. Preparation. — It is made from sulphuret of 
iron, as hydrochloric acid is made from common salt, 
and hydrofluoric acid from fluor spar. In the above 
process, sulphuret of iron furnishes the sulphur, and 

561. Explain the above process. 562. What is hydrosulphuric acid? 
563. How is it prepared ? 



HYDROSULPHURIC ACID. 273 

hydrated sulphuric acid, the hydrogen. The remain- 
ing elements unite to form sulphate of iron, which re- 
mains in solution. On account of the disgusting smell 
of the gas, it is best to prepare it only in small quanti- 
ties. 

564. Discoloration of Metals and Paints. — The 
blackening of silver watches and coins, in the vicinity 
of sulphur springs, is an effect of hydrosulphuric acid 
gas. Its discoloring effect may be illustrated, by pour- 
ing a little dilute sulphuric acid upon a few grains of 
sulphur et of iron, in a tea-cup, and holding a bright 
moist coin in the fumes. Its effect on paints may be 
shown by exposing a piece of paper, moistened with 
solution of sugar of lead, in the same manner. The 
white paper immediately assumes a dark metallic stain. 
Paper moistened with a solution of tartar emetic, takes 
a deep orange hue. This experiment is often varied, 
by drawing amusing figures on paper with lead 
solution, and bringing them out by exposure to the 
gas. 

565. Explanation. — The change of color in each 
case, is owing to the formation of a metallic sulphide, 
having a different, and generally a darker color. Zinc 
is not blackened, because its sulphide happens to be 
white. For this reason, chemical laboratories and 
other places where hydrosulphuric acid is likely to be 
evolved, should be painted with zinc paints, instead of 
those containing lead* 

5&i. What effect has it on metals, etc. ? 565. Explain the cause of the 
change of color. 



274 PRINCIPLES OF CHEMISTRY. 

566. Relations to Life. — Sulphuretted hydrogen, 
if inhaled in any considerable quantity, acts as a poison. 
Caution should therefore be observed in experiments 
with this gas. The mixture of gases which is given off 
from recently ignited coal, contains sulphuretted hydro- 
gen gas in large proportion, and owes its deleterious 
qualities, in considerable part, to this admixture. 

Ammonia, Spirits of Hartshorn. 

Symbol, H3N; Equivalent 11.) 

567. Description. — Ammonia is a colorless gas, of 
pungent smell, and alkaline properties. It is exhaled 
from volcanoes, and is a product of the decompo- 
sition of all vegetable and animal matter. Its mole- 
cule contains one atom of nitrogen to three of hydrogen. 

568. Production from its Elements. — Although 
nitrogen and hydrogen gases are the sole elements of 
ammonia, they cannot, under ordinary circumstances, 
be made to unite directly and form it. Heat does not 
stimulate their affinities sufficiently to bring about this 
result. Electrical sparks passed, for a long time, 
through a mixture of the gases, cause them to combine 
to a limited extent. 

569. Production from Nascent Elements. — Iron, 
at a high temperature, expels hydrogen from ordinary 

566. What is the effect of sulphuretted hydrogen on animals ? 567. 
W T hat is ammonia ? Where does it occur ? 568. What is said of its pro- 
duction from nitrogen and hydrogen ? 569. Production from its nascent 
elements. 



AMMONIA. 275 

hydrate of potassa, and nitrogen from nitre. If heated 
with both together, it expels both nitrogen and hydro- 
gen, and the two nascent elements unite, to form am- 
monia. The experiment may be performed by cover- 
ing bits of potash and nitre with iron filings, and heat- 
ing them in a test-tnbe. Another method of producing 
ammonia, through the agency of platinum sponge, is 
described under the head of Platinum. 

570. Preparation. — Ammonia is commonly made 
from salts that contain it, by using some strong base to 
retain the acid, and set the gas at liberty. Potash or 
lime may be used for this purpose. Intro- 167 
duce into a test-tube about half an inch of a 
stick of fused potash, and cover it with pow- 
dered sal-ammoniac. On the addition of water 
to dissolve them, ammonia will be immediately 
evolved. Pest the tube on the table, and place 

a wide-mouthed vial over it to collect the gas. ^ 
This gas cannot be collected over water, as it would be 
rapidly absorbed. It must therefore be collected 
over mercury, or by displacement as shown in the 
figure. 

571. Solution in Water. — Aqua Ammonias. — Bring 
the mouth of the vial filled with ammoniacal gas, 
quickly, into a bowl of water. The water will swallow 
up the gas so rapidly as to rise and fill the vial, pro- 
ducing a weak solution of ammonia or hartshorn. If 
only a small portion of water be allowed to enter, and 

570. How is ammonia commonly prepared ? 571. How is its solubility 
in water proved? 



276 



PRINCIPLES OF CHEMISTRY. 




the vial be then removed from the bowl and shaken, 
the hartshorn obtained will be comparatively strong. 

For the preparation 
of the solution in large 
quantity, the apparatus 
shown in figure 168 
may be used. Water 
will absorb 670 times 
its own bulk of ammo- 
niacal gas, forming the 
fluid known as aqua 
ammonia. Newly 
slaked lime may be sub- 
stituted for potash. 

572. A Miniature Fountain. — Fill a pint vial with 
ammonia, by the method above given, 
and immediately introduce, air-tight, 
into its mouth, a moist paper stopper 
with a bit of pipe-stem run through it. 
Then invert the bottle into a bowl of 
water. The absorption by the first por- 
tions of water that enter will be so com- 
plete as to produce a vacuum, into which more water 
will rise, in a jet, as represented in the figure. 

573. Alkaline Properties. — Bring the material for 
making ammonia into a tea-cup or similar open vessel. 
Hold a strip of litmus paper, previously reddened by an 
acid, in the gas, as it is evolved. The acid will be 




572. How may ammonia be employed to produce a jet of water? 
573. Explain its action on acids. 



PHOSPHURETTED HYDROGEN. 277 

neutralized by the ammonia, and the paper restored to 
its original color. Any substance which is very soluble 
and neutralizes strong acids, is called an alkali. As 
ammonia has this property, and is also volatile, it is 
therefore called a volatile alkali. The same experi- 
ment with litmus paper, may be also made with the 
hartshorn obtained in the last experiment. 

574. It fumes with Acid Yapors. — Moisten a piece 
of paper with strong muriatic acid, and wave it to and 
fro through the gas. White fumes are pro- 170 
duced by the union of the muriatic acid and 
the ammonia. In uniting, they form small 
particles of muriate of ammonia, or sal-am- 
moniac, in the air. It is of these that the 
fumes consist. It will be observed, that in 
this experiment the material from which the 
ammonia was originally prepared is reproduced. The 
same fumes are formed on waving a paper moistened 
with muriatic acid through the atmosphere of a stable. 
Ammonia is constantly evolved in such places, from the 
decomposition of animal matter. 

Phosphuretted Hydrogen. 

Symbol, H3P; Equivalent, 34. 

575. Description. — Phosphuretted hydrogen is a 
colorless gas, of an odor that has been compared to 
that of putrid fish. It is spontaneously inflammable 
by contact with the air. In the relative proportion of 
its elements, it corresponds with ammonia. This gas 

574. Its effect on acid vapors. 575. What is phosphuretted hydrogen ? 




278 



PRINCIPLES OF CHEMISTRY. 



is sometimes produced in the decay of vegetable and 
animal matters. The jack-o-lantern, or will-o-the-wisp, 
sometimes seen in swamps and grave-yards, is supposed 
to have its origin in the spontaneous production and 
combustion of this gas. 

576. Preparation. — Phosphuretted hydrogen is made 
from phosphorus, with the help of water and an alkali. 
Water furnishes the requisite hydrogen, if lime or pot- 
ash is at the same time present. Introduce into a 
small vial two-thirds full of water, a stick of ordinary 
fused potash, broken in pieces, and a bit of phosphorus 
of the size of a pea. On the application of heat, this 
gas is evolved. It is carried through a pipe-stem, and 
171 allowed to bubble up through 

water contained in a tea-cup 
or bowl, as represented in the 
figure. If the atmosphere is 
still, the bubbles, as they burst 
and inflame form beautiful 
white rings which rise in suc- 
cession into the air. These rings consist of particles of 
phosphoric acid, produced by the combustion of the phos- 
phorus which is contained in the gas. In order that the 
gas may be safely evolved, it is best to heat the vial in a 
tea-cup containing salt dissolved in three times its bulk 
of water. The addition of salt has the effect of raising 
the boiling point. The comparatively high tempera- 
ture required, may thus be obtained without exposure 
of the vial to the direct flame of a lamp. 

576. How is phosphuretted hydrogen prepared ? 




LIGHT CARBURETTED HYDROGEN. 279 

577. Explanation. — In the action which occurs in 
making phosphuretted hydrogen from potash, water, 
and phosphorus, the latter plays the part of an ex- 
tremely rapacious element. It makes no distinction in 
the objects of its appetite, but seizes upon both the oxy- 
gen arid hydrogen of the water, two substances as widely 
different from each other as possible. It forms with 
the one, phosphuretted hydrogen, and with the other, 
what might be called phosphuretted oxygen, but is, in 
fact, an acid. Potash is employed in the process, to 
promote the formation of this acid. In its absence, 
water resists the affinities of the phosphorus, and 
neither acid nor phosphuretted hydrogen is obtained. 

Compounds of Hydrogen with Carbon. 

578. Most of the compounds of carbon and hydro- 
gen belong to the vegetable world, and will therefore 
be more properly considered in the chapter on organic 
chemistry. Only two of them, which exist ready 
formed in nature, will be here mentioned. 

Light Carburetted Hydrogen. 

Symbol, C 2 H 4 ; Equivalent, 16. 

579. Description. — Light carburetted hydrogen is a 
colorless, inodorous, inflammable gas, about half as 
heavy as air. Its molecule contains two atoms of 
carbon to four of hydrogen. It is produced in ponds 
and marshes, by the decomposition of vegetable matter 

577. Explain the above process. 579. What is light carburetted hydro- 
gen ? Where does it occur ? 



280 



PRINCIPLES OF CHEMISTRY. 



172 




under water, as will be more fully explained in Part 
IV. From this circumstance it is also called marsh- 
gas. It may be collected 
by stirring up the mud 
under the mouth of a 
funnel leading into a 
jar or jug as shown in 
the figure. Mixed with 
other gases, it issues 
from fissures in coal 
mines, forming the fire-damp formerly so much dreaded 
on account of its explosive properties. As coal is of 
vegetable origin, the gas of the mines which proceeds 
from it is also traceable to the vegetable world. In some 
173 districts, particularly in regions where 

borings are made for salt, it issues from 
the earth in sufficient quantity to form 
the fuel required to boil down the brine, 
or even to illuminate villages. 

580. Preparation. — An impure, light 
carburetted hydrogen, is obtained from 
wood by simple heating. For this 
purpose, saw-dust or bits of shaving 
are heated in a test-tube. The gas may 
be burned in a jet as fast as formed. 
The product thus obtained is not pure, but mixed 

580. How is light carburetted hydrogen prepared ? 

* Boussingault has discovered that under the influence of direct sunlight the 
leaves of aquatic plants give off a notable proportion of carbonic oxide and carbu- 
retted hydrogen. He thinks that the carbonic oxide thus gven off maybe one cause 
of the unhealthinees of marshy districts. 




LIGHT CAEBUEETTED HYDROGEK. 281 



with, olefiant and other gases which make the flame 
more luminous. The pure gas may be made from 
strong vinegar, (acetic acid,) by the agency of heat and 
potash, as will be explained in the latter part of this work. 

581. Explosions in Mines. — Marsh gas forms, with 
air, an explosive mixture before alluded to, which is 
often the occasion of fearful accidents in mines. The 
experiment may be made with olefiant gas, which has 
the same explosive property. This property belongs, 
indeed, to most gases and vapors which contain hydro- 
gen ; as for example, to the vapors of ether, alcohol, 
camphene, and " burning fluid." 

582. Davy's Safety Lamp. — The distinguished 
English chemist, Davy, devised a method of security 

against these 
explosions. It 
consists in sur- 
rounding the mi- 
ners' lamp with 
wire gauze, 
which will ad- 
mit air through its insterstices, 

but will not let out flame to ignite 

the explosive atmosphere of the 

mine. The flame of the lamp is 

surrounded with glass to allow the 

light to be seen while the gauze 

protects the lamp from currents 





581. Explain the cause of explosion in mines. 582. Describe Davy's 
safety lamp. 



282 PRINCIPLES OF CHEMISTRY. 

of gas above or below. This effect may be illustrated, 
by holding down a piece of wire gauze upon the flame 
of a candle. If the gauze is fine, the flame will not 
pass through it. This effect is owing to the reduction 
of temperature which the wire occasions. The subject 
will be better understood by reference to the paragraphs 
which follow, on the nature of flame. 



Heavy Carburetted Hydrogen. Olefiant Gas. 

Symbol, C4H4 Equivalent, 28. 

583. Description. — Heavy carburetted hydrogen is a 
colorless gas, of peculiar sweetish odor, also known as 
olefiant gas. It is nearly twice as heavy as the light 
carburetted hydrogen just described, and contains twice 
the quantity of carbon. It forms a small proportion of 
the fire-damp of mines and salt borings, before de- 
scribed. The foul air left after the explosion of fire- 
damp is called after-damp. 

584. Preparation. — Heavy carburetted hydrogen is 
made from alcohol, by the decomposing action of sul- 
phuric acid. Bring into a test-tube a tea-spoonful of 
alcohol, with a little sand, and add four times as much 
oil of vitriol. On heating over a spirit lamp, the gas 
is evolved, and may be burned like the gas just de- 
scribed, at the mouth of the tube. The acid employed 
has the effect of retaining part of the elements of the 



583. What are the properties of olefiant gas ? 584. How is it pre- 
pared ? 



HEAVY CARBURETTED HYDROGEN. 283 

alcohol, 'and allows the rest to escape as olefiant gas. 
The reaction* is more fully explained under the head 
of organic chemistry. 

585. Illuminating Gas. — Gas for illumination is 
commonly prepared from bituminous coal. Such coal 
is principally composed of carbon and hydrogen. A 
portion of these elements pass off under the influence 
of a high temperature, in the form of gas. The pro- 
duct is rather a mixture of gases, among which light 
and heavy carburetted hydrogen are the principal. To 
illustrate this process fill the bowl of a tobacco pipe 
with pieces of bituminous coal not larger than peas ; 
cover the top with clay well pressed down, and place 
the bowl in a fire so that the stem may project. In a 
short time a dark-colored smoke will issue from the 
pipe stem to which set fire, and you will obtain a gas 
flame, producing a good light. If the heat is intense, 
coal tar will be produced at the same time. The illu- 
minating power of gas is principally derived from heavy 
carburetted hydrogen. Its quality, within certain 
limits, depends on the relative proportion of this con- 
stituent. 

586. Purification. — The gas as it rises, contains 
ammonia and sulphuretted hydrogen, two impurities 
which it is essential to remove. If the materials for 
making the gas are placed in a test tube the ammonia 
may be stopped in its passage, by a loose wad of 

585. How is illuminating gas made ? 586. How is it purified. 



*The term reaction, signifies, in chemistry, the mutual action of chemical agents. 




284 PRINCIPLES OF CHEMISTRY. 

of moistened paper ; the sulphuretted hydroge'n, by a 
176 similar wad, moistened with solution of 

sugar of lead. The papers having 
been introduced, the pipe-stem is fitted 
to the tube with a paper stopper, and 
the tube heated over the alcohol flame 
with the help of a blow-pipe. When 
the coal has become red hot, the gas 
will pass off in sufficient quantity to 
be ignited at the extremity of the tube. 

587. At the conclusion of the process, the upper wad 
contained in the tube will be found blackened by the 
sulphuretted hydrogen which it has retained. On re- 
moving the second one, it will be found to smell of 
ammonia. The presence of this body may also be 
shown, by the fumes which it yields with muriatic 
acid. 

588. Arrangements in Gas Works. — The process 
in gas works is essentially the same, as that above de- 
scribed. The coal is heated in iron retorts. The tar 
collects in pipes leading from it. Carbonate of ammo- 
nia is washed out by a jet of water, which plays in an 
enlargement of the pipe. Lastly, sulphuretted hydro- 
gen is removed by the retentive power of a metallic 
base, lime being generally employed for this purpose. 
From ten to twelve thousand cubic feet of gas are 
obtained from a ton of coal. 



587. How are the impurities shown ? 588. Describe the process in gas 
works. 




HEAVY CAKBUEETTED HYDROGEN. 285 

589. Collection and Distribution. — After purifica- 
tion, the gas is collected in large iron holders called 
gasometers, which are iron cylinders of great size. 
These may be represented by the 
inverted tumbler in figure 177. 
Gas pouring in from below would 
lift and fill it. If an orifice were 
made in the top, the tumbler would 
immediately settle into the water. 
The air would, at the same time, escape through the 
orifice. The distribution of illuminating gas, from 
public gas works, is effected on the same principle. 
The weight of the sinking gasometer, is sufficient to 
press it through pipes, to all parts of a large city. 

590. Gas from "Wood. — Gas may be made from wood 
by the same means above given. Only a moderate 
heat is required, in this case, to produce tar at the same 
time. Gas of higher illuminating power than that pre- 
pared from wood or coal may also be made from oil, fat 
or rosin. Even refuse vegetable substance may be em- 
ployed. A pound of dried grape skins have been found 
to yield 350 quarts of excellent illuminating gas. The 
dried flesh of animals has sometimes been used for its 
manufacture. 

591. Other Compounds of Carbon and Hydrogen. 
India-rubber, gutta-percha, naptha or rock-oil, coal-tar 
and oil of turpentine are other well-known compounds 
of carbon and hydrogen. 

589. How is illuminating gas collected and distributed? 590. How may 
gas be made from wood ? 591. What other compounds of carbon and 
hydrogen are mentioned ? 



286 



PRINCIPLES OF CHEMISTRY. 



Flame. 



592. Flame. — Nothing in nature is, to the unin- 
structed eye, more mysterious than flame. It is, seem- 
ingly, body without substance, and shape, without 
coherence. It is created by a spark, and annihilated 
by a breath. Invulnerable itself, it destroys whatever 
it touches. Divided and subdivided, it is still the same, 
yet endowed with the power of resolving other mate- 
rials into their elements. Chemistry resolves this mys- 
tery, and gives us the satisfaction of definite knowledge 
in its place. But, as in all similar cases, while satisfy- 
ing the understanding, it opens new fields to the 
178 imagination. The subject of combustion, as 

involved in flame, introduces us, for example, 
to a knowledge of the grand system of cir- 
culation of matter as set forth in the last 
chapter of this work. 

593. Structure of Flame. — Explana- 
tion. — Every lamp or candle is a gas factory, 
in which gas is first produced out of oil or 
fat, by the fire which kindles it, and after- 
ward by the heat of its own flame. A flame, 
if carefully observed, will be found to con- 
sist of three distinct parts ; a dark center, a 
luminous body, and a faint blue envelop. The dark 
center is filled with the gas as it arises from decompo- 
sition of the oil or fat of which the candle is composed. 




592. What is said of flame ? 593. Explain the structure of flame. 



FLAME. 



287 



In the luminous envelop the hydrogen and carbon are 
separated, the hydrogen first unites with the oxygen of 
the atmosphere and forms water, at the same time it 
produces an intense heat by which the liberated carbon 
in solid particles is raised to a red or white heat. As 
this heated carbon flows outward and upward until it 
meets a sufficient supply of atmospheric air it forms 
carbonic oxide, and at length, when folly oxidized, 
carbonic acid, assuming first a faint blue color, and in 
the form of carbonic acid becomino* entirely invisible. 

In the dark center no air or oxygen is found. In the 
luminous envelop there is an insufficient supply of oxy- 
gen which is principally taken up by the hydrogen 
because oxygen is more powerfully attracted by hydro- 
gen than by carbon. In the outer or 
blue envelop there is an abundant sup- 
ply of oxygen in a heated state and it 
attacks all bodies with great energy 
which are brought in contact with it. 

594. Oxygen essential to ordinary 
Combustion. — The student will already 
have found abundant evidence that air 
or oxygen is essential to ordinary com- 
bustion. A still more striking illustra- 
tion of the subject remains to be given. 
A phosphorus match, if suddenly intro- 
duced into the interior of a flame, notwithstanding the 
high temperature in its vicinity, is not ignited. The 




594. How is the nature of flame further illustrated ? 



288 PRINCIPLES OF CHEMISTRY. 

wood burns off, but the phosphorus of the match does 
not undergo combustion. The same principle may be 
illustrated by holding a match for a moment through 
the body of the flame. It is consumed at the sides, 
while the center remains unburned. 

595. Combustion without Oxygen. — It has "been 
shown in section 371 that many metals in a finely 
divided state take fire spontaneously in chlorine gas. 
The same effects are produced with bromine. If sul- 
phur is heated in a flask to its vaporizing point it forms 
a dark amber-colored vapor in which copper foil burns 
with great splendor, producing sulphide of copper. It 
is thus evident that oxygen is not in all cases necessary 
to combustion. The phenomena of light and heat 
which attend combustion depend on intense chemical 
action, and are not dependent exclusively upon any 
peculiar form of matter. 

596. Effect of Flame on Metals. — If a tarnished 
penny be held perpendicularly in the flame of a lamp 
or candle, the portion within the flame will lose its 
coating of oxide, while the exterior portions at the 
same time become more deeply oxidized, and conse- 
quently, darker colored. It is because there is an ex- 
cess of carbon • and hydrogen in the interior of the 
flame, to take oxygen from the metal, by their superior 
affinity, and pass off with it as gas or vapor. In the 
outside, on the other hand, there is an abundant supply 
of air to impart oxygen, or, in other words, to oxidize. 

595. Give examples of combustion without oxygen. 596. What is the 
effect of flame on metals ? 



FLAME. 



289 



By moving the coin to and fro after it is once thoroughly 
heated, the instantaneous conversion of metal into 
oxide, and oxide into metal, may be readily observed. 
A beautiful play of colors, like those upon a soap bub- 
ble, will be found to attend the transformation. The 
flame of a spirit lamp is, in some respects, preferable 
for this experiment. 

597. Oxidizing Flame. — The blue envelop of the 
flame, which, with the hot air adjacent, has the property 
of oxidizing metals, is called the oxidizing flame. 

598. Reducing Flame. — The body of the flame, 
which, with the heated gas within it, has deoxidizing 
effects, and reduces oxides again to the metallic form, 
is called the reducing flame. The * 
process of deoxidizing is called re- 
duction. 

599. The Blow-Pipe.— The pecu- 
liar effects of both the oxidizing and 
reducing flame, may be still better 
obtained by help of the simple 
mouth blow-pipe. A, B, C, figure 
180, shows the best form of the blow- 
pipe. At B is a chamber to retain 
the moisture from the mouth. The 
mouth-piece A, is often made of 
glass or ivory. A simple form of 
blowpipe is shown at a b. In want 
of a metallic tube, a common tobac- 



A 



a 
¥7 



U 




597, What is the oxidizing flame ? 598, What is the reducing flame ? 
99. Describe a blow-pipe of simple construction ° 

13 



290 



PRINCIPLES OF CHEMISTRY. 



181 



co-pipe, to the bowl of which a piece of a second stem 
is fitted, as represented in the figure, may be made to 
answer the purpose. With its aid, a lamp 
or candle flame is converted into a miniature 
blast furnace. The mouth is applied at the 
end of the long stem, while the shorter one 
carries the blast to the flame. The orifice 
of the latter should be extremely small. It 
may be so rendered, by filling with clay and 
then piercing it with a needle. 

600. Oxidizing Blow-Pipe Flame. — To oxidize with 
the blow-pipe, the flame, mixed with a large proportion 
of oxygen, is blown forward upon the metal, or other 
material, subjected to experiment. This is effected by 

introducing the extremity 
of the blow-pipe, a little 
within the flame. The air 
of the lungs becomes thus 
mixed with the rising gases. 
The result is a slender, 
blue flame, at the point of which, within its fainter blue 
envelop, the metal is to be held. A piece of lead, of 
the size of a grain of wheat, placed on charcoal, hol- 
lowed out for the purpose, and exposed to the flame, 
will soon be converted into litharge. The oxide will 
be recognized by the yellow incrustation which it forms 
upon the charcoal support. 

601. Keducing Blow-Pipe Flame. — To convert 




600. How is the blow-pipe used for oxidation ? Give an example. 601. 
How is the blow-pipe used for reducing metals ? 



FLAME. 291 

oxides into metals, or in other words, to reduce with 
the aid of the blow-pipe, the gases of the flames are 
blown forward, upon the substance, mixed with lit- 
tle air. The extremity iss 
of the blow-pipe is ^y^^^^^ :::::s= ^ 
placed against the outer ^<^^^ ::::=::==5 *^l 
wall of the flame, a lit- -SS^-^"^ gjjjpj jjj ^ 
tie higher than in 

the previous case. The IllLiiJiiiB 

flame thus produced is yellow, and of the shape repre- 
sented in the figure, The oxide to be reduced, is to 
be placed within the yellow body of the flame, but 
near its termination. The litharge produced in the 
last experiment, may be re-converted, by this means, 
into metallic lead. 

602. Heating- by the Blow-pipe Flame. — The con- 
centration of flame upon a small object by means of 
the blow-pipe produces a very great degree of heat, 
which is employed for soldering metals, and for other 
important purposes in the arts. The rapid supply of 
oxygen to the burning gas in the flame causes this great 
increase of heat. 

603. The Oxygen Blow-pipe. — If a bladder, V, 
filled with oxygen, furnished with a stopcock, ?', and a 
small tube, t, is employed to blow the lamp as shown 
in figure 184, the heat will be much greater than where 
common air or air from the lungs is used. The heat 
obtained by this means is sufficient to melt wire of 

60S. What is said of the heat produced by the blow-pipe ? 



292 



PRINCIPLES OF CHEMISTRY. 





platinum. The bladder is filled with oxygen gas from 

the jar, <?, 

with its 

stopcock, s, 

as shown in 
figure 185, standing over the pneumatic 
cistern. A still greater degree of heat 
is obtained by means of the oxyhydro- 
gen blow-pipe described in the next 
section. 

604. OXYHYDROGEN BlOW-PIPE. 

The compound or oxyhydrogen blow-pipe, as com- 
monly constructed, consists of two gasometers, contain- 
ing, the one, oxygen, and the other hydrogen gas; 
186 tubes, r and s, leading from 

these, are brought together at 
their extremity, and the two 
gases are burned in a single 
jet. One tube is inclosed 
~s within the other so that the 

two gases do not mingie until they reach the extremity 
of the tube. By this arrangement all danger of ex- 
plosion is avoided. The heat thus produced is the most 
intense that has ever been realized except by Galvanic 
means. Iron, copper, zinc, and other metals, melt and 
burn in it readily ; the former, with beautiful scintilla- 
tions, and the latter, with characteristic colored flames. 
With a sufficiently constant flame platinum also may 
be readily fused. The apparatus for making oxygen 

604. Describe the oxyhydrogen blow-pipe. 




FLAME. 



293 



187 




and hydrogen as represented in the figure, furnishes a 
simpler means of obtaining similar results. An abund- 
ant flow of hydro- 
gen is required, and 
a pint bottle should, 
therefore, be em- 
ployed in its prepa- 
ration. To retain 
it free from water, 
which would tend 
to reduce the heat 
of the flame, a lit- 
tle cotton may be introduced into the bowl of the pipe 
through which it passes. In evolving the oxygen, only 
a part of the tube should be heated at a time lest the 
gas should be too rapidly evolved. 

605. Flameless Lamps. — Place a little ether in a 
wine-glass and suspend in it a coil of platinum wire 
heated to readness, combustion of the ether will pro- 
ceed without flame and the heat evolved will keep the 
platinum wire red hot for hours, 
or as long as vapor of ether is 
supplied with free access of air. 
This experiment may be varied 
by suspending the coil of plati- 
num wire heated to redness over 
the wick of a lamp filled with ether. The wire will 
glow emitting a steady light without flame. To com- 



188 





605. Describe the flameless lamp. 



294 PRINCIPLES OF CHEMISTRY. 

mence tlie combustion in either case, the wire must be 
heated to redness. 

606. Explanation. — The heated wire raises the tem- 
perature of the ethereal vapor to the point where it can 
combine with oxygen, but the heat is not sufficient to 
produce the rapid combustion essential to the produc- 
tion of flame. That is to say, the heat is sufficient to 
keep the platinum coil red hot but not to make the 
vapor of ether red hot. 

607. NoN-LiTMiNOTTS Flame. — A jet of burning hydro- 
gen, like the philosopher's lamp, section 519, gives out 
so little light that it is almost invisible in the daytime. 
Burning alcohol also emits but very little light. If 
common illuminating gas passes up through a tube 
open both at bottom and top and is ignited at the top, it 
burns with an almost invisible flame, although it gives 
out a very high degree of heat. Bunsen's lamp is con- 
structed on this principle. Even the flame of the oxy- 
hydrogen blow-pipe emits scarcely any light although 
the heat is so great as to cause the most refractory 
metals to melt like wax. 

608. Incandescence. — Combustion always implies 
chemical action with the evolution of heat, and this 
heat is attended with a certain quantity of light ; but 
a body may evolve heat and light without undergoing 
combustion or any chemical change. Platinum wire, 
fibers of asbestos, or a piece of lime exposed to the 
strong heat of invisible flame, as burning iydrogen, 

606. Explain the operation of the flameless lamp. 607. How may we 
obtain a flame nearly invisible ? 608. What is incandescence ? 



FLAME. 295 

may be heated to whiteness so as to evolve both heat 
and light of surprising intensity. This condition is 
called ignition or incandescence. The body evolves 
light as the result of its high temperature without its 
molecules being materially altered in their physical or 
chemical relations. The greater the amount of heat 
which a body can sustain without physical change the 
more intense will be the light emitted. Solids, liquids 
and gases may all be rendered incandescent by a suffi- 
cient degree of heat, but gases require for this purpose 
a higher temperature than can be obtained by ordinary 
means, and volatile liquids follow the same law. The 
vivid luminosity and varied color of lightning is proba- 
bly dependent on the incandescence of the gases and 
vapors of the atmosphere. 

If we pass a gentle current of air through a porce- 
lain tube at a white heat, .the air issuing from it is not 
luminous even in the dark, but if finely divided solid 
particles are projected into the escaping jet of heated 
air, they are immediately rendered luminous. 

609. Carbon as a source of Illumination. — Car- 
bon is the most infusible substance known and uncom- 
bined with other elements it never assumes a gaseous 
form. Carbon is therefore the most valuable source of 
illumination yet known. Tallow, oils and burning fluids 
of all kinds owe their illuminating powers to the car- 
bon which they contain, while the hydrogen and other 
elements serve only to elevate the temperature of the 
carbon. 

609. Why is carbon the most valuable source of illumination ? 



296 PRINCIPLES OF CHEMISTRY. 

610. Calcium Light. — When the non-luminous flame 
of the oxy hydrogen blow-pipe is directed upon a cylin- 
der of lime (oxide of calcium) a more intense light is 
produced than by any other artificial means except the 
most powerful Voltaic current. This light is sufficient 
to illuminate whole streets of cities and is of great value 
for light-houses. This is often called the Drummond 
light, from the name of the inventor. 

611. Color of Flame. — Flame assumes different 
• colors according to the chemical nature of the different 

substances projected into it, modified by the tempera- 
ture to which they are elevated. The salts of lithia 
and strontia impart a red color to flame ; baryta and 
boracic acid impart a green tint ; salts of copper give a 
blue color ; soda flame is yellow, while the flame of po- 
tassa is of a beautiful violet color. Between the poles 
of a powerful Voltaic battery zinc gives a blue color in 
strata or bands ; antimony a lilac color ; mercury a 
pale blue ; cadmium an intense green ; arsenic a mag- 
nificent lilac ; and bismuth a variety of colors under- 
going rapid changes. 

612. Spectra of Metals. — It has been already stated 
that the flames of different metals produce characteris- 
tic colored bands in a spectra produced by their own 
light (46). Sodium, for example, produces in the spec- 
trum a double yellow line and copper a band of brilliant 
green. A flame containing several metals gives, at one 
and the same time, the characteristic bands of all. If 

610. What is the calcium light ? 611. What causes the varied colors 
of flames ? 



HEAT. 29T 

these metallic flames be employed as media instead of 
sources of light, and if the light of an electric lamp be 
passed through them, they occasion dark stripes in the 
spectrum precisely corresponding to the colored bands 
before described. In other words, while transmitting the 
larger portion of the light, they absorb from it precisely 
that class of rays which when used as the sources of light 
they originate. Figuratively speaking, instead of paint- 
ing their images they now cast their shadows in the 
spectrum. The correspondence between the dark lines 
which a given metal thus occasions by absorption and 
the bright lines which it produces by radiation is, per- 
fect in numbers, breadth, and position. The shadow, 
as we have termed it, equally with the image, is pecu- 
liar and characteristic. Let us illustrate by an exam- 
ple. About sixty bright lines have been determined as 
belonging to the iron flame when used as a source of 
light. When light from an electric lamp is passed 
through a flame containing iron, sixty dark lines pre- 
cisely corresponding are found in the spectrum. These 
sixty dark lines with their peculiar grouping are there- 
fore no less than the bright lines, characteristic of iron. 
If found in any spectrum it may be inferred that the 
light which produces it has passed through flame or 
vapor containing that metal. 

613. The Solar Atmosphere. — These lines charac- 
teristic of iron are found with all their peculiarities 
among the dark lines of the solar spectrum (45). It is 

3. What is said of the constitution of the solar atmosphere ? 



298 PRINCIPLES OF CHEMISTRY. 

hence inferred that the solar light on its way to the 
earth has passed through a vapor containing this metal. 
And as this could only occur within its own atmos- 
phere, the conclusion is warranted that iron is a con- 
stituent of the photosphere or luminous envelope of the 
sun. 

The dark lines belonging to calcium, magnesium, so- 
dium, chromium, and certain other metals are also 
found in the solar spectrum. Like those of iron they 
are found there in the precise position required to ren- 
der them characteristic. These metals also are, as a 
consequence, inferred to be constituents of the solar at- 
mosphere.* 



CHAPTER II. 



METALS, 



614. Definition of Metals. — Metals are opake bodies 
possessing a peculiar luster and a great readiness to 
conduct heat and electricity. Fifty metals are known 
to chemists, but many of them are of no special interest 
to the ordinary student. 

614. What are metals ? 



* For further information on this curious subject, the student is referred to the 
Smithsonian Eeport for 1861, and to Brande & Taylor's Chemistry. 



METALS. 299 

615. Physical Properties of Metals. — Color. The 
color of most metals is white, gray or bluish, but gold is 
yellow and copper red. 

Opacity. While most metals are- opake, gold may 
be beaten so thin as to transmit green light, or blue 
if alloyed with silver. 

Hardness and JBrittleness. Most metals are regarded 
as hard bodies, but potassium and sodium are soft like 
wax. Some other metals, as lead, may be readily cut 
with a knife. Antimony, arsenic and bismuth are 
easily pulverized. Zinc is brittle at common tempera- 
tures, but at the temperature between 200° and 300° it 
may be rolled into thin plates or drawn into wire. 

Malleability. Gold may be hammered so thin that 
200,000 leaves are required to measure an inch. Some 
metals become hard and brittle by hammering and 
require to be softened by heating before the hammer- 
ing can be continued. Gold is the most malleable of all 
metals ; after it, in the order of their malleability, stand 
silver, copper, aluminum, tin, cadmium, platinum, lead, 
zinc and iron. 

Ductility. Platinum may be drawn into wire not ex- 
ceeding 3 o,^o oth of an inch in diameter. The order of 
ductility is, gold, silver, platinum, iron, copper, alumi- 
num, zinc, tin and lead. Aluminum, a very light metal, 
only about two and a half times as heavy as water, has 
recently been drawn into wire so fine that it is made into 
lace work, epaulettes, embroideries and head-dresses. 

615. Mention some of the physical properties of the most common 
metals? 



300 PRINCIPLES OF CHEMISTRY. 

Tenacity ', or strength, is another important property 
of metals. In reference to tenacity, metals may be 
arranged as follows : iron, copper, palladium, platinum, 
silver, gold, zinc, tin and lead. Iron has the greatest 
tenacity of all metals, being capable of supporting 25 
times as great a weight as a lead wire or rod of the 
same dimensions. An iron wire one-tenth of an inch 
in diameter will support 550 pounds, copper 302, plati- 
num 274, silver 187, gold 150, zinc 100, tin 35 and lead 
28 pounds. 

Fusibility. All the metals may be melted by a suffi- 
cient degree of heat. Mercury is fluid at all ordinary 
temperatures and only becomes solid at 40° below zero 
of Fahrenheit's scale, while platinum requires for its 
fusion the highest heat of the oxyhydrogen blow-pipe. 

Volatility. Mercury passes into vapor at any tem- 
perature above 40°. Potassium, sodium, zinc and 
cadmium are volatile at a red heat ; gold and silver 
waste by evaporation in melting and there is no doubt 
that all the metals would be volatile with the highest 
degree of heat. 

Relation to Electricity and Magnetism. Silver is 
the best conductor of electricity and mercury the poor- 
est. All metals conduct electricity best when cold. 
Platinum becomes red hot by the transmission of a 
current of electricity that produces scarcely any effect 
upon a silver wire of the same dimensions. Next to 
silver copper is the best conductor of electricity. Mer- 
cury is used for uniting the poles of Voltaic batteries, 
not because it is a good conductor but because it forms 



METALS. 301 

a very complete connection between the different parts 
of the apparatus. 

It has long been known that iron is attracted by the 
magnet and that steel may be rendered permanently 
magnetic. "When a bar of iron is placed between the 
poles of a magnet it places itself parallel to the axis 
of the magnet ; the same effect is produced with nickel, 
cobalt and platinum. But other metals when properly 
suspended take a direction at right angles to the mag- 
netic axis. Such substances are called diamagnetics. 
Yarious solid liquids and gases are found in both these 
divisions. Iron, nickel, cobalt, manganese, chromium, 
palladium, platinum and osmium are magnetic^ while 
bismuth, antimony, zinc, tin, cadmium, sodium, mer- 
cury, lead, silver, copper, gold and arsenic are dia?nag- 
netic. 

Crystallization. Many metals on cooling from the 
fluid state, or during decomposition from chemical com- 
binations, assume the crystalline form. If melted metal 
is allowed to concrete externally and the crust is then 
pierced and the fluid metal is poured out, the cavity so 
formed will generally be found lined with crystals. 
Bismuth treated in this manner appears in the form of 
cubical crystals. Copper, gold, silver and iron become 
brittle and lose much of their tenacity when they be- 
come crystallized. Extreme cold and rapid vibration 
cause the axles of railroad cars to assume a partial crys- 
talline texture, which often occasions serious accidents. 

616. Classification of Metals. — The metals may 

616. How may the metals be classified ? 



302 PRINCIPLES OF CHEMISTRY. 

be arranged in groups or classes, according to their 
affinity for oxygen. Those which tarnish or rust 
most readily, come first in order, while the last group 
is made up of the noble metals, which retain their 
brilliancy unimpaired. 

617. Class I. — Potassium and Sodium. — These two 
metals combine with oxygen so eagerly, as to tarnish 
instantaneously on exposure to the air. They even 
seize on that which is contained in water and expel its 
hydrogen. The hypothetical metal ammonium, is de- 
scribed in connection with this group, because of the 
similar properties of its compounds. 

618. Class II. — Barium, Strontium, Calcium, Mag- 
nesium. — The metals of this class show their affinity 
for oxygen in the same manner as those of Class I. 
But they are inferior, in this respect, to both potassium 
and sodium. Either of these metals can deprive them 
of the oxygen with which they may have combined. 

619. Class III. — Aluminum, Manganese, Iron, 
Chromium, Cobalt, Nickel, Zinc, Cadmium. — The 
metals of this class tarnish less rapidly than the fore- 
going, by exposure to the air. In order that they may 
decompose water, and appropriate its oxygen, they re- 
quire the stimulus of an acid, or of heat. Except in 
the case of manganese, the heat must be sufficient to 
convert the water into steam. Strictly speaking, there- 
fore, they do not decompose water, but steam. 

620. Class IV. — Tin and Antimony. — Tin and anti- 

617. Describe the metals of Class I. 618. Describe Class II. 619. De- 
scribe Class III. 620. Describe Class IV. 



POTASSIUM. 303 

mony tarnish less readily than the metals of the previ- 
ous class. To enable them to decompose water, and 
appropriate its oxygen, they require the stimulus of a 
red heat. An acid, or moderate heat will not suffice. 

621. Class V. — Bismuth, Copper and Lead. — Al- 
though copper and lead become tarnished, or covered 
with a thin film of oxide, rather more readily than the 
metals of the last two groups, their affinity for oxygen 
under other circumstances is less. This is evident in 
the fact that a red heat enables them to decompose 
water and appropriate its oxygen but feebly. Acids 
will not suffice. Bismuth doos not tarnish so readily 
as copper or lead. 

622. Class VI. — Mercury, Silver, Gold, and Plat- 
inum. — The metals of this class do not tarnish, and do 
not decompose water under any circumstances. Even 
if made to combine with oxygen by other means, they 
yield it again very readily, and return to the condition 
of metals. They are called the noble metals. 

CLASS FIRST. 
Potassium. 

Symbol, K (Kalium) ; Equivalent, 39 ; Specific Gravity } 0.865. 

623. Description. — Potassium is a bluish white 
metal, lighter than water, and soft, like beeswax. Like 
wax, it is also converted by the heat of an ordinary fire 



621. Describe Class V. 622. Describe Class VI. 623. What is potas- 
sium ? Where is it obtained ? 



304 PRINCIPLES OF CHEMISTRY. 

into vapor. Water and acids dissolve it readily. The 
metals of this and the following groups, were discov- 
ered by Sir Humphrey Davy, early in the present 
century. They were first produced by the Galvanic 
process. Potassium is a constituent of many rocks, of 
all fertile soils, and of the ashes of plants. The more 
important minerals which contain it, are alum, feldspar, 
and mica. As these rocks are disintegrated to form 
soil, the potash they contain becomes soluble and is 
taken up by plants. From the ashes of plants we 
obtain nearly all our supply of potash, which is an 
oxide of potassium. 

624. Preparation. — Potassium is made from carbon- 
ate of potassa, by removing its carbonic acid and oxy- 
190 gen. This is accomplished by heat- 

ing intensely with charcoal, which 
removes both in the form of car- 
bonic oxide. The metal which ac- 
companies the gas, in the form of 
vapor, is condensed by naptha, instead of water. The 
process is essentially the same as that for preparing 
j^iosphorus, but requires apparatus beyond the reach 
of the ordinary experimenter. Cream of tartar, if 
heated, is converted into a nearly suitable mixture of 
carbonate of potassa and pure carbon, for this purpose. 
The tartaric acid is decomposed into carbonic acid and 
free carbon, the carbonic acid unites with the potash 
and each atom of carbonate of potash has an atom of 
carbon in contact with it in a free state. The carbon 

634. How is potassium prepared? 




POTASSIUM. 305 

is more intimately mixed with the potash than it could 
be by any mere mechanical means. A small quantity 
of charcoal, in fragments, is added, and the whole 
heated intensely in an iron retort. 

625. Combustion on Water. — Potassium, if thrown 
upon water, is immediately ignited and burns 
beautiful violet flame. Strictly 

speaking, it is not potassium which Ac^Sp 

burns, but the hydrogen which it <^^ssgil=si> 
sets at liberty. Owing to its strong ^* -*^5jJsjjbssl^- 
affinity for oxygen, it takes this element from water, 
liberating, and at the same time kindling, the hydrogen 
with which it was before combined. The color of the 
flame is due to a small portion of vaporized potassium 
which burns with this gas as it is evolved. The glo- 
bule of metal used in this experiment gradually dis- 
appears, because the potassa which it forms by uniting 
with oxygen is soluble in water. 

626. Setting a Eiver on Fiee. — Put two or three 
small pieces of potassium in a teaspoonful of ether and 
throw the contents into a pail of water, the whole 
surface of the water will appear in a blaze. By mak- 
ing the experiment on a larger scale, we may accom- 
plish the feat of " Setting a river on fire" During the 
Crimean war Mr. Mcintosh proposed to destroy the 
shipping and harbor of Sebastopol by firing bombshells 
filled with ether and containing pieces of potassium. 
The use of such shells would doubtless have been very 



625. Explain the action of potassium on water. 626. How can a river 
be set on fire with potassium ? How could potassium be used in war ? 



306 PRINCIPLES OF CIIEMISTIiY. 

destructive, but the British government feared that 
carelessness on the part of the sailors might lead to the 
destruction of their own shipping also. In trying this 
experiment, even on a small scale, the student should be 
extremely careful and keep at a distance from the water 
lest the potassium should fly into and injure the eye. 
Care also should be taken lest the ether should take 
fire from a lamp or gas-light, if any is near. 

627. Combustion in Cakbonio Acid. — Potassium has 
192 such a powerful affinity for oxygen that 

it will even take it from carbonic acid 



i 



gas. Place a small piece of potassium 
in an iron spoon, and after heating it, 
insert it in a jar of carbonic acid gas, 
as shown in figure 192, it readily takes 
fire and burns with a purple flame. 

628. Uses of Potassium. — Potassium has not been 
applied to important uses in the arts, but is a valuable 
agent in the hands of the chemist. It is a key which 
unlocks many substances from the prison in which 
nature has confined them. Through its agency, brill- 
iant metals may be obtained from lime, magnesia, and 
common clay. 

629. This effect depends on the superior affinities of 
potassium, which enable it to appropriate oxygen, chlo- 
rine, and other substances, with which the above and 
several other metals are combined in nature, and to 
isolate the metals themselves. The potassium is at the 

627. How can potassium be made to burn in carbonic acid? 628. 
State the uses of potassium. 629. On what does its action depend ? 



SODIUM. 307 

same time converted into oxide or chloride of potas- 
sium, both, of which are soluble in water, and may be 
washed away from the metal which has been produced. 



Sodium. 

Symbol, Na (Natrium) ; Equivalent, 23 ; Specific Gravity, 0.9t2. - 

630. Properties. — The metal sodium is similar in its 
properties to potassium. It is prepared by similar 
means, from carbonate of soda, and may be employed 
by the chemist, for the same purposes. In color it 
resembles silver but like potassium it readily tarnishes 
on exposure to the air. It softens at 122°, melts at 
200°, and at a white heat it is changed into a color- 
less vapor. It burns in the air with a yellow flame. 
Thrown upon water, it decomposes it, without however 
igniting the hydrogen which is evolved.* Sodium is 
readily soluble either in water or acids. 

631. Sodium occurs in the mineral kingdom, but its 
great storehouse is the ocean from whence it is ob- 
tained in the form of common salt. It occurs also in 
sea-weeds and largely abounds in animal fluids. It is 
perhaps the most abundant metal upon the globe, as it 
constitutes about two-fifths of sea salt and is a large 
ingredient of rocks and soils. 

630. Sodium — description, preparation, solvents, and properties ? 
631. Where is sodium found ? 



* If sodium is -wrapped in paper, to prevent waste of heat, it burns with flame* 
like potassium, upon water. 



308 PRINCIPLES OF CHEMISTRY. 

632. Uses of Sodium. — Sodium is now prepared in 
large quantities, in France, as a material to be used in 
the manufacture of the metal aluminum. Its cost, a 
few years since, was ten dollars an ounce. It can now 
be procured in Paris for less than a dollar per pound. 

Ammonium. 

Symbol, H 4 N ; Equivalent, 18. (Hypothetical.) 

633. Ammonium is a compound of nitrogen and hy- 
drogen, which is presumed to be a metal. Its molecule 
contains one atom of nitrogen, to four of hydrogen. 
If a metal, it differs from all others, in being a com- 
pound, and not a simple element. There are, however, 
good grounds for believing in the existence of such a 
compound gaseous metal. The chloride of ammonium 
is named in accordance with this view. Judging from 
the properties of the salt, w^e might reasonably expect, 
by removal of its chlorine, to obtain from it a substance 
with metallic properties, as well as from chloride of 
sodium or common salt. But the experiment does not 
justify the expectation. As soon as the chlorine is re- 
moved, the metal also decomposes, and a mixture of 
gases is the result. The principal ground for attribu- 
ting a metallic character to the combination of nitrogen 
and hydrogen gases, in the preparation above stated, 
has been already indicated. They supply, in certain 
salts, the place which known metals fill in the other and 

632. For what purpose is it used ? 633. What is said of ammonium ? 




AMMONIUM. 309 

similar compounds. A confirmatory experiment is de- 
scribed in the succeeding paragraphs. 

634* Ammoxium Amalgam. — Another ground for 
believing in the existence of ammonium with true 
metallic properties, is found in the following experi- 
ment : If chloride of ammonium is mixed with an 
amalgam of sodium and mercury, a double 193 
decomposition ensues. The chlorine and 
sodium unite to form common salt, while 
the mercury combines with the ammonium 
without losing its metallic luster. But there 
is no instance of this retention of metallic properties in 
the combination of mercury or any other metal with 
any non-metallic substance. The inference is that am- 
monium is a metal. But any attempt to isolate it by 
removal of the mercury from the amalgam is ineffectual. 
As soon as this is done the ammonium is resolved into 
gaseous ammonia and hydrogen. This change takes 
place, indeed, spontaneously. 

635. In performing the above experiment, a small 
globule of potassium or sodium is heated with a thim- 
ble full of mercury in a test-tube, and a strong solution 
of sal ammoniac added. The mercury increases in bulk 
without losing its luster, and continues to expand until 
it fills the tube or glass with a light pasty amalgam. 

634. State another reason for believing in the existence of a metal am- 
monium. 635. How is the amalgam experiment performed. 



310 PRINCIPLES OF CHEMISTRY. 

CLASS SECOND. 
Barium. 

Symbol, Ba; Equivalent, 69; Specific Gravity, 1.5. 

636. Barium is an ingredient of the well known and 
abundant mineral, sulphate of baryta or heavy spar, 
which is found in beautiful white tabular crystals, and 
is much used mixed with carbonate of lead for white 
paint. Barium is a soft silvery metal, easily tarnished 
in the air. It is made from baryta, by the process 
already described in the section on potassium. It may 
also be procured by passing potassium or sodium in 
vapor over baryta heated to redness in an iron tube. 
Its compounds, including baryta, from which it is pre- 
pared, are hereafter described. Barium is soluble in 
most acids. It decomposes water at ordinary tempera- 
tures, evolving hydrogen and forming a solution of 
oxide of barium called baryta. 

Strontium. 

Symbol, Sr; Equivalent, 44 ; Specific Gravity, 2.5. 

637. Strontium is very similar to barium, but darker 
in color. It is produced from strontia by a similar pro- 
cess. Its solvents are also the same as for barium, 
strontium decomposes water without combustion, set- 
ting free hydrogen, and forming a soluble protoxide. 

636. In what form does barium occur ? How is it separated ? What 
are its solvents ? 637. Strontium— description, production and solvents ? 



MAGNESIUM. 311 

Calcium. 

Symbol, Ca; Equivalent, 20; Specific Gravity, 1.5 1 

638. The metal calcium is similar to barium, and is 
made from lime by the use of potassium, as before 
described. Its solvents are the same as those of the 
metals above-named. 

Magnesium. 

Symbol, Mg; Equivalent, 12, Specific Gravity, 1.74. 

639. Magnesium is a soft, silvery, white metal, pre- 
pared from its chloride instead of the oxide, by means 
of potassium. Water oxidizes magnesium as it does the 
other metals of this class, but converts it into an insol- 
uble white powder. Most acids dissolve it. None of 
the metals of this class have as yet been applied to any 
useful purpose in the arts, except magnesium. Magne- 
sium is malleable and ductile, and volatile like zinc. 
It does not decompose water and oxidizes but slowly 
even in moist air. It is readily dissolved by acids. 

640. Magnesium Light. — When magnesium is heat- 
ed in the air it burns with great brilliancy, evolving a 
white light of great intensity. A magnesium wire 
one twenty-fifth of an inch in diameter coiled upon a 
spool is moved by clockwork and projected into the 
flame of an alcohol lamp. It burns with a remarkably 

638. Calcium — description, production and solvents ? 639. Magne- 
sium—description, preparation, solvents and occurrence ? 640. Describe 
the magnesium light. 



312 PRINCIPLES OF CHEMISTRY. 

even and tranquil flame, especially adapted for photo- 
graphing by night or in any dark or subterranean 
locality. Such a light as here described is equal to 74 
stearine candles. At present its cost, which is about 
ten dollars an hour, forbids its use except for the most 
important purposes. But there is no doubt that means 
will yet be found of producing magnesium at prices 
which will allow of the extensive employment of this 
magnificent light, so portable and so convenient for use 
in the arts. A light of almost any degree of intensity 
might be obtained by burning larger wires, or by burn- 
ing several smaller wires at the same time. 

CLASS THIRD. 
Aluminum. 

Symbol, Al; Equivalent, 14; Specific Gravity, 2.56 to 2.67* 

641. Aluminum derives its name from alum of which 
it forms an important ingredient. The ruby, sapphire, 
topaz, corundum and emery, all owe their peculiar 
hardness to alumina which is an oxide of aluminum. 
Aluminum is also an essential ingredient in common 
clay and therefore a part of all fertile soils and the 
rocks that produce them. By its discovery every clay 
bank is converted into a mine of valuable metal. Alu- 
minum is a bluish white malleable and ductile metal, 
similar in appearance to silver and possessing about the 
same degree of hardness. Its specific gravity when 

641. In what minerals does aluminum occur? What are its properties ? 



ALUMINUM. 313 

cast is two and a half times greater than water, and 
2.67 when rolled. It is only about one-third as heavy 
as iron. It fuses at the same temperature as silver, and 
preserves an untarnished surface in the air. It does 
not decompose water, even with the aid of boiling heat. 
Alloyed with iron, it protects the latter from the action 
of the air. 

642. Preparation. — Aluminum is prepared by pass- 
ing chloride of aluminum in a state of vapor over 
melted potassium or sodium. The latter metal is com- 
monly employed. The fluoride may also be used in the 
process, or the mineral cryolite^ which is a compound of 
fluoride of aluminum with fluoride of potassium. The 
latter constituent interferes in no wise with the process. 
The method of preparing the chloride, as a material for 
the production of the metal, is given in the section 
on chlorides. 

643. Action of Acids. — Muriatic acid is its proper sol- 
vent, and forms with it a colorless solution. Nitric acid 
whitens it, if previously dipped into strong potash or 
soda. Dilute sulphuric acid is without action. Alum- 
inum may be poured from one vessel to another in a 
fused condition without oxidation. Like silver it may 
be deposited by the galvanic process. 

644. It is highly sonorous, and therefore adapted to 
the manufacture of bells. This metal is now prepared 
in France at about ten dollars per pound. The French 
government propose to use it for helmets and cuirasses, 

642. How is aluminum prepared ? 643. What is the, action of acids on 
it ? 644. Mention its other properties. 

14 



314 PRINCIPLES OF CHEMISTRY. 

for which it is especially fitted by its lightness and 
tenacity. For other uses of aluminum, see Alloys, § 

747. 

Manganese. 

Symbol, Mn ; Equivalent, 28 ; Specific Gravity, 8. 

645. Manganese. — Manganese is a gray brittle metal, 
produced from its oxide by heating with charcoal. It 
is found in nature as black oxide of manganese and as 
a constituent of many other minerals. It enters also 
in small proportions into the composition of soils. 
Diluted sulphuric and muriatic acids are its proper sol- 
vents, forming with it pale rose-colored solutions. 
The black oxide serves as a source of oxygen, and is 
also employed in the preparation of chlorine gas. It 
is also used in the production of artificial amethysts, 
and also to impart to glass the same violet tint. An 
alloy of manganese and iron is harder and more elastic 
than iron alone. Manganese is used as a flux in the 
preparation of cast steel, and it furnishes a useful mor- 
dant to the calico printer when precipitated upon the 
fiber in the form of a brown hydrate. Manganese is 
speedily oxidized when exposed to the air ; it must there- 
fore be preserved in sealed tubes or under naphtha. 
The pure metal is slightly magnetic and is hard enough 
to scratch steel. 



645. Manganese— description, production, occurrence, solvents and 
uses ? 



iron. 315 

Iron. 

Symbol, Fe, (Ferruni) ; Equivalent, 28 ; Specific Gravity, 7.84. 

646. Description. — Pure iron is nearly white, quite 
soft, exceedingly malleable and highly tenacious. It 
may be rolled into leaves so thin that a bound book 
containing forty-four such leaves shall be only one- 
fifteenth part of an inch in thickness. In the condi- 
tion of perfect purity it is never seen except 

in the chemist's laboratory. Even the purest _U 

iron of commerce contains traces of other 

substances. Dilute sulphuric and muriatic 

acids are its proper solvents, forming with it 

green solutions. The addition of nitric acid 

or chlorine changes the color to red. Iron 

may be readily burned, as has already been shown in 

the section on oxygen. 

647. Occurrence. — Iron is a most abundant metal, 
but is rarely or never found in the metallic form, ex- 
cepting as meteoric iron. In this condition it is always 
alloyed with nickel. The latter metal being uniformly 
combined with it in masses known to have fallen to the 
earth as meteor s^ its presence in similar masses discov- 
ered on the surface of the earth, is regarded as evidence 
of their metoric origin. Iron is a constituent of a great 
variety of minerals, of all soils and plants, and even of 
the blood of animals. The peroxide of iron, the mag- 

646. Mention some properties of iron. 647. Does metallic iron occur 
in nature ? 



316 



PRINCIPLES OF CHEMISTRY. 



netic oxide, and clay iron stone, are its principal ores. 
Whole mountains of tlie magnetic oxide exist in Mis- 
souri and in Sweden. 

648. Production. — Iron is produced from its ores, 
which are impure oxides, by 
heating with lime, to remove 
the impurity, and at the 
same time with coal and the 
gases proceeding from it, 
to remove the oxygen. A 
smelting furnace, such as is 
represented in the figure, 
being previously heated, is 
charged with the material in 
layers, and the heat main- 
tained by the coal of the 
mixture. In the upper part 
of the furnace the materials 

are thoroughly dried. As they gradually settle, they 
become more thoroughly heated, and meet carbonic 
oxide from the coal below, which robs the iron of its 
oxygen, and converts it into particles of metal. Still 
lower down, the lime combines with the earthy por- 
tions of the ore, forming a liquid glass. The reduced 
iron thus liberated, collects, fuses, and sinks to the bot- 
tom of the furnace. From this point it is run off into 
channels of sand, where it hardens into pig iron. 

649. Explanation. — The ordinary impurities of the 




648. How is iron produced ? 649. How is the slag formed ? For what 
uses may it be employed ? 



IRON. 



317 



ore are clay and quartz or silica. Lime has the prop- 
erty of forming, with both of these, a fusible glass or 
slag, which floats upon the melted iron. This material 
is of a light green color. But it may be otherwise 
colored to suit the taste, and cast into slabs, columns, 
architectural and parlor ornaments of great beauty. 
The process by which its brittleness is removed, and the 
slag adapted to the above uses, has not been made pub- 
lic. 

650. Cast Iron. — The pig or cast iron, as it is called, 
which is thus obtained from the furnace, is not pure 
iron, but a compound of iron w T ith carbon. It has ob- 
tained four or five per cent, of this element from the 
coal with which it w^as reduced. The addition of car- 
bon to its composition causes iron to melt more readily. 
But for its absorption, the metal would not have be- 
come sufficiently soft to flow from the furnace. Car- 
bon has also the opposite property of making iron 
harder and more brittle when cold. Castings of agri- 
cultural implements and 
other objects, are made by 
remelting the pig iron, and 
pouring it into moulds of 
the required shape. 

651. "Wrought Iron. — 
"Wrought iron is made from 
cast iron, by burning out 

its carbon. This is done in what is called a reverbera- 




650. Give the composition and properties of cast iron. 651. How is 
wrought iron made ? 



318 PRINCIPLES OF CHEMISTRY. 

toiy furnace, such as is represented in the figure. The 
carbon is burned out by the surplus air of the flame, 
which is made to play upon the molten iron. From 
the constant stirring which is essential, such a furnace 
for refining iron is called a puddling furnace. The 
metal becomes stiffer as it loses carbon, and is then 
hammered and rolled into bars. 

652. Iron Wire. — The bar of wrought iron thus 
produced, is highly malleable and ductile, and may be 
rolled into sheets, or drawn into the finest wire. "Wire 
is made by drawing a wrought iron bar, by machinery, 
through a hole of less than its own diameter, and re- 
peating the process until the required degree of fine- 
ness is attained. Wrought iron loses its tenacity, and 
becomes granular and brittle, like cast iron, by long 
jarring. This effect sometimes occurs in the wheels and 
axles of railway carriages, and is the occasion of seri- 
ous accidents. 

653. Welding. — Wrought iron becomes soft at a cer- 
tain heat, without melting. This property, which adds 
greatly to its usefulness, belongs to no other metal ex- 
cepting platinum. In the soft state, two pieces maybe 
united by hammering. This process is called ivelding. 
The surfaces to be welded are sprinkled with borax, to 
protect them from the air, which would form a crust of 
oxide of iron and prevent a perfect contact. Its fur- 
ther action is explained in the chapter on salts. Beside 



652. Mention an important property of wrought iron. How is iron 
wire made ? 653. How is wrought iron welded ? 



IRON. 319 

borax, other materials having a similar effect are fre- 
quently employed. 

654. Steel. — Steel may be made from cast iron by 
burning out half its carbon. Or it may be made from 
wrought iron, by returning half of the carbon which 
was removed in its preparation. The latter is the pro- 
cess generally pursued. It consists in burying the 
wrought metal in iron boxes containing charcoal and 
heating it for several days, until combination with a 
certain portion of the carbon is effected. 

655. Annealing. — The hardness of steel depends 
upon the rate at which it is cooled. By heating it to 
redness, and cooling it slowly, it is rendered as soft and 
malleable as wrought iron. This process is called an- 
needing. By cooling it very suddenly, it becomes as 
hard and brittle as cast iron. Steel instruments are 
commonly hammered out of the soft steel, and subse- 
quently hardened. 

656. Tempering Steel. — Steel hardened as above 
described is too hard and brittle for most uses. Any 
portion of its original softness and tenacity may be re- 
turned to it, by reheating and slow cooling. To restore 
the whole, a red heat would be required. To give back 
part, and make a steel so tough as not to break readily, 
yet sufficiently hard for cutting, a lower temperature is 
employed. This process is called tempering. The sort 
of temper imparted depends upon the degree of heat 
which has been employed. 

654. How is steel made ? 655. How is steel made soft or hard ? 656. 
How is steel tempered ? 



320 PRINCIPLES OF CHEMISTRY. 

657. The proper temperature is ascertained by the 
color which the steel assumes when heated. Tools for 
cutting metal are heated until they become a pale yel- 
low ; planes and knives, to a darker yellow ; chisels and 
hatchets, to a purplish yellow ; springs, till they be- 
come purple, or blue. In each case they are afterward 
slowly cooled. These colors are owing to a film of 
oxide of iron, which is formed upon the steel under the 
influence of heat. The tint is different, according to 
the thickness of the film. All these colors may be seen 
by heating a knitting-needle in the flame of a spirit lamp. 
Where it is hottest it becomes blue, and this color 
shades off into pale yellow on either side, like the col- 
ors of the solar spectrum. 

658. Writing upon Steel. — Nitric acid corrodes 
steel dissolving the iron but leaving the carbon which 
it contains in the form of a dark gray stain. "Writing 
and ornamental shading upon polished steel are per- 
formed in this manner. Nitric acid leaves only a whit- 
ish green stain upon iron which may by this means be 
distinguished from steel. 

659. Iron as a Medicine. — Pure iron in a finely 
divided state is used in medicine as a tonic. For this 
purpose it is reduced from the oxide by the action of 
hydrogen. 

660. Iron reduced by Hydrogen. — Pure oxide of 
iron is heated in a bulb of hard glass, A, figure 197, 



657. How is the proper heat ascertained ? 658. What is the method of 
writing upon steel ? 659. How is iron used as a medicine ? 660. De- 
scribe the method of reducing iron by hydrogen 



CHROMIUM. 



321 



197 




by the flame of a spirit lamp ; a current of hydrogen 
is passed through a glass tube filled with chloride of 
calcium to re- 
move all tra- 
ces of mois- 
ture, after 
which it pass- 
es through 
ah carrying 
with it the 

oxygen which it takes away from the heated oxide. 
Pure iron thus obtained in a finely divided state takes 
fire spontaneously in the open air. It must therefore 
be kept in sealed tubes. If this operation is conducted 
in a porcelain tube at a high temperature the product 
may be kept in glass bottles without oxidation and is 
then in a suitable form to be used as a medicine. 

Chromium. 

Symbol, Cr; Equivalent, 26.2*7 ; Specific Gravity, 6.8. 

661. Description. — Chromium is a grey metal, not 
readily tarnished and so hard as to scratch glass. It 
is of no use in the arts in the metallic form. It is 
found in combination with iron, as chromic iron, and 
also in beautiful crystals, as red -chromate of lead. It 
may be prepared from its oxide, like iron, by heating 
with charcoal. Its compounds are much valued as 
coloring materials both in painting on porcelain and in 



661. Chromium— description, production, ores, solvents, and uses ? 



322 PRINCIPLES OF CHEMISTRY. 

calico printing. Chrome green and chrome yellow are 
valuable pigments. Its proper solvents are the same 
as those of iron. The solutions of this metal are 
green. 

Cobalt. 

Symbol, Co ; Equivalent, 29.5 ; Specific Gravity, 8.95. 

662. Description. — Cobalt is another grey metal, 
tarnishing but slightly in the air. It is somewhat 
malleable. It is found combined with arsenic, as arsen- 
ical cobalt, and in some other minerals. As metal, it is 
without useful application in the arts. It may be pro- 
duced like iron, by heating with charcoal, but is more 
readily reduced by hydrogen. A current of this gas 
being made to pass through a hot tube containing the 
oxide, it combines with oxygen, and passes off with it 
as water, leaving the metal in the form of a fine pow- 
der. Its proper solvents are the same as those of iron 
and chromium. Many of the compounds of cobalt are 
remarkable for the beauty and brilliancy of their color, 
and are used as pigments. The solutions of cobalt are 
pink. The oxide is employed for imparting a blue color 
to glass. 

Nickel. 

Symbol, Ni; Equivalent, 26.5; Specific Gravity, 8.82. 

663. Description and Properties. — Pure nickel is 
a brilliant, silver white metal, hard and ductile, surpass- 

662. Cobalt— description, production, occurrence, solvents, and uses ? 
663. Nickel — description, production, ores, solvents, and uses ? 



zinc. 323 

ing even iron in tenacity. Nickel is not much affected 
by the air at ordinary temperatures. It is found in 
combination with copper in the mineral called copper 
nickel. It may be prepared by either of the methods 
used for cobalt. Its proper solvents are the same as 
those of the last four metals. The solutions of this 
metal are green. Nickel is principally used in the 
preparation of the alloy called German silver. This 
imitation of silver is brass rendered -white by the pro- 
portion of nickel which it contains. The alloy is com- 
posed of one hundred parts of copper, sixty of zinc, 
and forty of nickel. The Chinese use an alloy consist- 
ing of 8 parts copper, Q\ of zinc, and 3 of nickel. 

Zinc. 

Symbol, Zn; Equivalent, 32; Specific Gravity, 6.8. 

664. Description. — Zinc is a bluish white metal 
readily tarnished in moist air. It is brittle at ordinary 
temperatures, and converted into vapor at a red heat. 
If heated somewhat above the temperature of boiling 
water, it can be rolled into sheets. At a higher tem- 
perature, from 300° to 400° it again becomes brittle 
and may be pulverized in a mortar. It melts at 770° 
and is volatile at a bright red heat. Sulphuric and 
muriatic acids dissolve it readily, forming colorless 
solutions. It is not found native. The red oxide, and 
the carbonate, called calamine, are among its more im- 
portant ores. 

664. Zinc— description, ores, and solvents ? 



324 



PRINCIPLES OF CHEMISTRY. 



665. Production. — Zinc is produced from its oxide 
by heating with charcoal to remove the oxygen, or, in 
other words, to reduce it. When made from the carbon- 
ate, the ore is previously roasted, to expel its carbonic 
acid and bring it to the state of oxide. As the metal 
is volatile at the heat required in its reduction, an ordi- 
nary furnace, such as is used for making iron, cannot 
be employed in the process : the metal would be lost 
in vapor. It is therefore obtained by a process of dis- 

198 tillation. The roasted ore mixed 

with powdered charcoal is placed 
in a covered crucible, a, which 
is placed in a furnace; a tube, 
e, passes from near the top of 
the crucible downward through 
the bottom of the crucible and 
furnace to a vessel of water, d, 
in which the vapor of zinc as it 
issues from the crucible is con- 
densed. The metal thus produced contains some impu- 
rities, consisting of iron, lead, arsenic and cadmium 
some of which are separated by re-distillation. The 
carbonic oxide produced in the process at the same time, 
escapes into the air. It will be observed, that the pro- 
cess is essentially the same as that for producing potas- 
sium and phosphorus, as before described. Acids dis- 
solve zinc, forming colorless solutions. 

666. Action of Heat and Air. — Zinc may be burned 




665. How is zinc produced ? Why is a clay retort used ? 666. How 
may zinc be burned? How melted ? 




zinc. 325 

by heating it on charcoal in the blow-pipe flame. It 
melts, and converts itself rapidly in the process into 
white oxide of zinc. If an intense heat 199 

is employed, the vapors of the metal 
burst through the crust and burn 
to oxide, with a brilliant greenish 
flame. When zinc is burned in considerable quantity, 
in a highly heated crucible, the oxide forms flakes in 
the air to which the name of lana philosophica or phi- 
losopher's wool, was given by the alchemists. The oxide 
of zinc thus formed is collected and used as a pigment 
instead of white lead. It is cheaper than lead, not 
poisonous, it is not blackened by bilge water or sul- 
phuretted hydrogen, because its compounds with sulphur 
are white. Zinc is the only metal which forms white 
compounds with sulphur. The metal may be melted 
over a spirit lamp, in an iron spoon. 

667. Uses of Zinc. — Zinc is principally employed in 
the form of sheet zinc, for roofing and similar purposes. 
It is also used, like tin, as a coating to protect iron 
chains and other objects from rust. The coating is 
effected by plunging the iron into molten zinc, which 
forms an alloy upon its surface. The iron and zinc thus 
combined act as a Yoltaic circle, and the oxygen which 
would otherwise attack and rust the iron goes to the 
zinc and forms an oxide of zinc. The iron is thus pro- 
tected from rust as long as any clean surface of zinc 
remains not oxidized. The iron thus coated is some- 
times called Galvanized iron, though without reason, as 

667. Mention the uses of zinc ? 



326 PRINCIPLES OF CHEMISTRY. 

is evident from the above process, since no Galvanic 
action was employed in preparing this coating of zinc. 
Solutions of zinc are sometimes used to prevent the 
decay of wood, and to render it less combustible. It 
has also been employed with success, as a substitute for 
copper, in sheathing vessels. 

Cadmium. 

Symbol Cd; Equivalent, 56 ; Specific Gravity, 8.6. 

668. Cadmium is found in some ores of zinc, and 
being more volatile than zinc the greater part passes 
over with the first portions of distilled metal. Cadmi- 
um is a white metal resembling tin and so soft that it 
leaves a trace upon paper. It is malleable and ductile, 
melts at 442°. It is chiefly interesting on account of 
the alloys it forms with other metals. 

CLASS FOUETH. 
Tin. 

Symbol, Sn; (Stannin;) Equivalent, 56; Specific Gravity, 7.28. 

669. Description. — Tin is a brilliant white metal, 
very soft and malleable, and not easily tarnished. 
"When a bar of tin is bent, it gives a peculiar grating 
sound, fancifully called the cry of tin. This is a con- 
sequence of the friction of the minute crystals of tin of 
which it is composed. Its only ore is an oxide, called 
tin stone, of which Cornwall, England, is the principal 

G68. Describe the source, appearance and properties of cadmium. 
669. Describe the metal tin. From what ore is it made ? 



zinc. 327 

locality. The purest tin is obtained from the island of 
Banca, in the Dutch East Indies. This beautiful metal 
is one of those which have been longest known to man, 
as it is mentioned in the Books of Moses. 

670. Production. — Tin is produced, like iron and 
most other metals, by heating its oxide with carbon. 
The materials are heated in a small blast furnace. The 
carbonic oxide produced in the fire, as before explained, 
is the reducing agent. It takes the oxygen from the 
ore, and passes off with it as carbonic acid, while the 
metal fuses and runs to the bottom of the furnace. By 
heating tin before the blow-pipe, it is rapidly converted 
into white oxide. 

671. Action of Acids. — Tin resists weak acids 
remarkably. Dilute muriatic and sulphuric acids, 
which dissolve most of the metals before described, 
act upon it but feebly. The concentrated acids dis- 
solve it with comparative ease. Its solution, although 
less poisonous than those of lead, is still injurious to 
health. Acid food should, therefore, never be allowed 
to stand for a long time in tin vessels. The solutions 
of tin are colorless. 

672. Nitric acid acts upon tin with energy ; 
but, like a ferocious animal that destroys 
without devouring its prey, leaves it undis- 
solved. It converts it into a white insolu- 
ble powder of oxide of tin, with the evolution of the 
usual red fumes. This case is an exception to the 

670. How is tin produced ? 671. How do acids act on tin ? 672. What 
is the action of nitric acid ? 




328 PRINCIPLES OF CHEMISTRY. 

usual action of nitric acid. One portion of the acid 
commonly acts to produce oxide, while another portion 
dissolves the oxide formed. The experiment for the 
solution of tin may be made with tin-foil, in a tea-cup 
or test-tube. 

673. Aqxia-regia, it will be remembered, is a mixture 
of nitric and muriatic acids. In most cases they act, 
as before described, in concert to dissolve metals that 
neither can dissolve alone. They act thus, also, upon 
tin, in small portions. But if larger quantities are em- 
ployed, the mixture grows warm, and the nitric acid, 
as if stimulated beyond restraint, attacks the metal for 
itself, and converts it, as when it acts alone, into a white 
powder. 

674. Coating Pins. — Common brass pins are coated 
by boiling with cream of tartar and tin-foil or bits of 
tin. The acid of the tartar acts as a solvent. Tin is 
then deposited on the more electro-positive brass, as in 
cases of galvanic decomposition. At every point where 
brass, tin and the liquid are in contact, a small Galvanic 
battery is in fact produced. 

675. Ornamenting with Tin. — In India tin is ap- 
plied instead of silver to steel and iron by way of 
ornament. The tin is melted and while still liquid is 
agitated in a box until it has become solid ; the fine 
powder thus procured is separated from the coarser 
particles by suspension in water, and is made into a 
thin paste with glue ; it is then applied in the desired 

673. What is the action of aqua regia on tin ? 674. How are pins coated 
with tin ? 675. How is tin used for ornamental purposes in India ? 



ANTIMONY. 329 

pattern ; when perfectly dry it is burnished, and after- 
wards varnished ; its brilliancy is thus preserved un- 
changed. 

676. Tin Wake. — Tin is cast in various forms, for 
culinary and chemical utensils. A little lead is added 
to give it greater toughness. Common tin ware is made 
of sheet-iron coated with tin. The coating of the 
metal is effected by dipping well cleaned sheet-iron 
into molten tin. 

677. Crystalline Tin. — Tin has a great tendency to 
assume a crystalline form. The structure may be ob- 
served on washing the surface of ordinary tin plate 
with aqua-regia, to remove the thin coating of oxide. 
It may be still better seen if a tin plate is heated over 
a lamp until the coating melts, then suddenly cooled and 
afterward cleaned as above directed. The whole sur- 
face is then found to be covered with beautiful crystal- 
line forms. 

Antimony. 

Syrribol, Sb; (Stibium;) Equivalent, 122; Specific Gravity, 6.7 

678. Description. — Antimony is a bluish white and 
highly crystalline metal which does not tarnish in the 
air. It is so brittle that it may be readily reduced to 
powder. The ore from which the metal is produced is 
the grey sulphuret, or antimony glance. 

679. Production. — Antimony may be obtained from 

676. How is tin plate made ? 677. How may the crystalline structure 
of tin be seen ? 678. Describe the metal antimony. From what ore is 
it obtained ? 679. How is antimony produced ? 



330 PRINCIPLES OF CHEMISTRY. 

its oxide by the usual process of reduction. The sul- 
phuret is first partially converted into oxide by roasting, 
and still further by carbonate of soda, which is added 
in the subsequent process. It is then mixed with char- 
coal, and intensely heated in crucibles. At a white 
heat the metal fuses and sinks to the bottom. The 
soda added in the process exchanges its oxygen for the 
remaining sulphur of the ore. 

680. Action of Heat and Air. — If heated before 
the blow-pipe, antimony soon melts, and burns with a 
white flame. It is at the same time converted into 
oxide. A portion of the oxide escapes into the air, 

while the rest forms a white coating 
upon the charcoal support. At the 
high temperature which is here pro- 
duced, the affinity of the metal for 
oxygen is so stimulated, that the molten globule, will 
continue to burn, even if removed from the flame. By 
directing a stream of air upon it, from a pipe-stem, the 
combustion may be maintained until the globule is en- 
tirely consumed. 

681. If the molten globule is allowed to fall upon 
202 the floor, it immediately divides into hun- 

, \ \ , / / dreds of smaller globules which radiate in 
^^ik^-"" a H directions, leaving each a distinct track 
-^V;'r$S>. °f white oxide behind it. 

/ 7/l\ i% " 682. Action of Chlorine. — A shower of 
fire may be produced by sprinkling fine powder of 




680. How may antimony be burned ? 681. Describe an experiment with 
the molten globule. 682. What is the action of chlorine on antimony ? 



BISMUTH. 331 

antimony into a vial containing chlorine gas. The metal 
is hereby converted into a white smoke of chloride of 
antimony. In its relations to the principal acids, anti- 
mony resembles tin. Its solutions are colorless. 

683. Uses of Antimony. — The principal use of 
antimony is in the preparation of alloys, to be hereafter 
described. Among these, type metal is the most im- 
portant. Many of the compounds of antimony, like 
other poisonous substances, are used with advantage in 
medicine. Tartar emetic is one of these medicinal com- 
pounds containing antimony. 

CLASS FIFTH. 
Bismuth. 

Symbol, Bi ; Equivalent, 210 ; Specific Gravity, 9.8. 

684. Description. — Bismuth is a brittle, crystalline 
metal of a reddish white color. It is used in making 
certain alloys. Like antimony it can be readily ground 
to powder. Crystals of bismuth may be obtained by 
the method described in the section on Sulphur, 
as represented in the figure. Nitric acid is its 
proper solvent and forms with it a colorless 
solution. Bismuth is found native, forming 
threads of metal in quartz rock Its most productive 
localities are in Saxony. 

685. Production. — The metal is procured from the 

683. What are the principal uses of antimony ? 684. Bismuth— descrip- 
tion, solvents, and occurrence in nature. 685. How is bismuth pro- 
duced ? 





332 PRINCIPLES OF CHEMISTRY. 

rock winch contains it, by simply heating in inclined 
tubes. At a comparatively moderate temperature the 
bismuth fuses and runs down into vessels placed to re- 
ceive it. 

686. Effect of Heat and Air. — The same experi- 
ments before the blow-pipe, and with molten globules, 

which were described in the case of 
antimony, may be made with bis- 
muth. The only difference is, that 
the metal does not burn with flame, 

and that the coating of oxide on the charcoal is yellow, 

instead of white. 

687. Uses of Bismuth. — Its principal use is in the 
preparation of alloys, to be described hereafter. One 
of them has the remarkable property of fusing in boil- 
ing water. Several compounds of bismuth are used in 
medicine ; the sub-nitrate is also employed as a cos- 
metic. This use of it is quite hazardous, as certain 
gases which are often present in the air, have the effect, 
as will be hereafter seen, of changing its color to a deep 
brown or black. 

Copper. 

Symbol, Cu, (Cuprum); Equivalent, 32; Specific Gravity, 8.8. 

688. Description. — Copper is a red, malleable, and 
highly tenacious metal. It tarnishes in the air, but is 
less injured by rust than iron, and therefore more dura- 



686. What is its action before the blow-pipe ? 687. What are the uses 
of bismuth ? 688. Copper— description, ores, solvents ? 



COPPER. 



333 



ble. Mtric acid is its proper solvent, and forms with 
it a green solution. Copper is found in abundance, in 
the metallic condition, on the southern shore of Lake 
Superior. It is chiseled out, in masses, from the rocks 
which contain it. The metal is more commonly ob- 
tained from a mineral called copper pyrites, which is 
a double sulphuret of iron and copper, it is also found 
as pure sulphuret, red oxide, and carbonate. Minute 
traces of copper are found in human blood. 

689. Production. — Copper is prepared from the im- 
pure sulphuret, by first 
burning out the sulphur in 
the air ; and secondly, heat- 
ing with charcoal to remove 
the oxygen which has taken 
its place. Sand is at the 
same time added, to form 




a floating slag with the oxide of iron, and thus remove 
it from the molten copper. The oxide of iron thus re- 
moved, is derived from the sulphuret of iron which is a 
usual constituent of copper ores. 

690. Both of the above processes of roasting and 
heating with charcoal and sand, must be several times 
repeated before pure metallic copper is obtained. It 
is to be remarked that the formation of a slag which 
shall remove this iron, depends on the fact that its oxide 
is by no means so easily reduced as copper. Being 



689. State briefly the mode of production. 690. State further particu- 
lars of the process. 



334 PRINCIPLES OF CHEMISTRY. 

once brought into the state of oxide, it remains in this 
condition and unites with the silicic acid of the sand. 

691. Action of Heat and Air. — At a high temper- 
ature, copper is readily oxidized in the air. Its oxida- 
tion may be observed by holding a copper coin in the 
flame of a spirit lamp, as described in the section on 
Flame. The iridescent hues observed in the experi- 
ment, are owing to the varying depth of oxide on dif- 
ferent portions of the coin. By long continuation of 
the process, the whole surface is converted into black 
oxide. If it is sooner suspended, and the coin plunged 
into cold water, a coating of red oxide containing less 
oxygen is obtained. 

692. Uses of Copper. — Copper is used for a variety 
of purposes for which iron would be less suitable on 
account of its rapid oxidation. Its employment in 
sheathing ships, is an example. It is also a constituent 
of various alloys, to be hereafter described. Among 
these, all gold and silver coins, and the metal of gold 
and silver plate are included. Copper wire is used in 
telegraphic cables for conducting electricity, being a 
better conductor than any other metal except silver. 

693. The copper of commerce often contains minute 
quantities of arsenic, iron and lead, and sometimes tin 
and silver. Copper may be obtained in a state of per- 
fect purity by decomposing a solution of sulphate of 
copper by means of the Yoltaic battery ; it is then de- 



691. What is the effect of heat and air ? 692. Mention some of the 
rses of copper. 693. How may pure copper be obtained ? 



LEAD. 335 

posited in coherent plates upon the negative electrode as 
in the process of copying medals or in electrotyping. 

694. Bronzing Copper Vessels. — Copper vessels, 
such as tea-urns, are often superficially coated with 
oxide, or hronzed to give them an agreeable appear- 
ance and to prevent tarnish. The copper surface is 
cleaned, and then brushed over with peroxide of iron 
(generally colcothar) made into a paste with water, or 
with a very dilute solution of acetate of copper; heat 
is then cautiously applied in a proper furnace or muffle 
until it is found on brushing off the oxide that the sur- 
face beneath has acquired a proper hue. 

Lead. 

Symbol, Pb, (Plumbum); Equivalent, 104; Specific Gravity, 11.4 

695. Description. — Lead is a bluish grey metal, ex- 
tremely malleable, and readily tarnished in the air. It 
is heavier than any other of the metals mentioned in 
this work except mercury, gold and platinum. ISTitric 
acid is its proper solvent, forming with it a colorless 
solution. The principal ore of this metal is galena or 
sulphuret of lead. Lead is also found as carbonate, 
sulphate, and phosphate of lead. 

696. Production. — Lead is obtained from the sulphu- 
ret by heating it with iron, to remove the sulphur. A 
mixture of metallic lead and sulphuret of iron is thus 



694. How is a bronze color given to copper vessels ? 695. Lead — de- 
scription, ores and solvents. 696. How is lead obtained ? 



336 



PRINCIPLES OF CHEMISTRY. 



206 




produced, from which the lead separates by its greater 
specific gravity. If the oxide of lead could be readily 

obtained the reduction by 
charcoal would be as appli- 
cable here as in the case of 
other metals. 

697. A second Method. 
— Another method, is to 
heat the sulphuret with a 
portion of sulphate. The 
sulphate has a large supply of oxygen, while the sul- 
phuret is destitute of this element. The two may be 
mixed in such proportions that they will together con- 
tain just enough oxygen to carry off all the sulphur as 
sulphurous acid. This result having been accomplished 
by heat, the pure metal of both remains behind. As 
a preparation for this process, a portion of sulphuret is 
converted into sulphate by heating in a reverbaratory 
furnace. Both parts of the process are in practice 
united ; a moderate heat with abundant air being first 
supplied, a portion of sulphate is produced. This is 
afterwards more highly heated, with the undecomposed 
sulphuret which remains. 

698. Action of Air and Heat. — If lead is heated 
before the blow-pipe in the oxidizing 
sss flame, it melts and disappears. The 
charcoal support becomes at the same 
time covered with yellow oxide of 



207 




697. Explain another method, 
before the blow-pipe ? 



What occurs when lead is heated 



LEAD. 337 

lead or litharge. The grey coating which at first forms 
upon the lead, is an oxide containing less oxygen. If, 
on the other hand, litharge is heated in the reducing 
flame, it is converted into metal. 

699. Action of Water. — Water, with the help of 
the air which it always contains, acts sensibly upon lead 
and becomes in consequence poisonous. This action of 
water is most decided when it contains no foreign mat- 
ter. On being conducted through leaden pipes, it be- 
comes therefore more impure as a consequence of its 
very purity. 

700. The presence of sulphates and certain other 
salts, such as are usually contained in spring water, 
prevents this effect. Those substances the presence of 
which in water we are accustomed to regret as im- 
purities, thus become our most efficient protectors 
against the poisonous effects of lead. 

701. But this rule is not without exception. Certain 
substances seem to increase the action. It is therefore 
always prudent where it is proposed to conduct water 
through leaden pipes, to ascertain by direct experiment, 
whether the particular water in question acts upon the 
lead or not. 

702. Illustration. — The difference in the action of 
pure water upon lead, and that which contains foreign 
substances in solution, may be readily proved by ex- 
periment. For this purpose, bright slips of lead; may 



699. What is the action o£ water on lead ? 700. W T hat prevents this 
action ? 701. Do imparities always protect ? 7Q3. Etescrjpe the experi- 
ment with lead and distilled water. 



338 PRINCIPLES OF CHEMISTRY. 

be placed in two tumblers, the one containing rain 
water, and the other well or spring water. The former 
will soon become turbid while the latter remains un- 
affected. 

703. The presence of lead in the former case may be 
still more strikingly shown, by adding to the water a 
few drops of a solution of hydrosulphuric acid. The 
formation of a dark cloud will show the presence of 
lead and indicate the danger to be apprehended. 

704. Lead Tree. — Dissolve some crystals of sugar 
of lead in thirty or forty times their bulk of water, and 
fill a vial with the solution. A strip of zinc hung in 

the vial will branch out in a beautiful arbor- 
escence of metallic lead. It may be neces- 
sary to clarify the solution by the addition 
of a little clear vinegar or acetic acid. A 
day or two will be required for the comple- 
tion of the experiment. The effect depends 
on the superior affinities of zinc for acetic 
acid. The zinc takes away acid and oxygen from suc- 
cessive portions of the sugar of lead, and leaves the 
particles of lead subject to the laws of crystallization. 
At the same time, the zinc having acquired possession . 
of the acid and oxygen comes into solution as acetate 
of zinc. A similar arborescence is produced in a solu- 
tion of silver by metallic mercury. 

705. Manufacture of Shot and Bullets. — Shot 
are prepared by pouring melted lead through perforated 

703. How may the presence of lead be better shown ? 704. Describe 
the lead tree and the reason of its production. 705. How are shot made ? 




MERCURY. 339 

iron vessels. A small quantity of arsenic is added to tlie 
lead to increase its fluidity when melted that it may be 
free to take a perfectly spherical form in falling. The 
drops are made to fall from a great height, that they 
may become cooled and solidified in their descent. 
They are canght in water that their shape may not be 
impaired. Having been assorted by means of seives, 
they are polished in revolving casks containing a small 
portion of black lead or plumbago. When lead is 
slowly cooled it contracts during solidification ; in bul- 
lets, therefore, there is generally a cavity which inter- 
feres with the rectilinear passage of the ball. Im- 
proved conical balls are therefore pressed in dies to 
make them perfectly solid throughout, by which the 
accuracy of flight is greatly increased. 

706. Other Uses of Lead. — In the form of sheet 
lead this metal is applied to a variety of familiar uses. 
It is also largely employed in the manufacture of lead 
tubing. It is a constituent of various alloys, among 
which pewter and type metal are the more important. 

CLASS SIXTH. 
Mercury. 

Symbol, Hg, (Hydrargyrum); Equivalent, 100 ; Specific Gravity, as a solid, 
14; as a liquid, at 32°F., 13.596 ; as vapor, 6.9 times heavier thanair. 

707. Description. — Mercury is a white fluid metal of 
high luster and beauty. It retains the fluid condition 

706. Mention other uses of lead. 707. Mercury— description, solvents, 
ores, discoveries. 



340 PRINCIPLES OF CHEMISTRY. 

at all ordinary temperatures. It becomes solid at 40° 
below zero, and boils at 660°. Nitric acid is its proper 
solvent. When pure mercury is shaken with water, 
ether, sulphuric acid or oil of turpentine, or rubbed 
with sugar, chalk, lard, or conserve of roses, it is re- 
duced to a gray powder which consists of minute mer- 
curial globules blended with the foreign body. "When 
this is removed they again unite into fluid mercury. 
In mercurial ointment (a mixture of lard and mercury) 
the globules of mercury are so small they cannot be 
discerned by the naked eye. If a solution of corrosive 
sublimate is precipitated by protochloride of tin, the 
liberated mercury forms so fine a precipitate that it is 
perfectly black and requires several hours to collect 
into shining globules. Mercury is sometimes found in 
the metallic form, but more commonly as the sulphuret 
or cinnabar , which is its principal ore. It is said that 
the mines in Mexico were accidentally discovered by a 
native hunting among the mountains. Laying hold of 
a shrub to assist him in his ascent, he tore it up by the 
roots, and a stream of what he supposed to be liquid 
silver flowed from the broken ground. 

708. Sources of Mercury. — The most productive 
mines of mercury are those of Almaden in Spain. It 
is also obtained from Mexico, California, Peru, China 
and Japan. The principal ore of mercury is the sul- 
phuret called cinnabar. It also occurs as a chloride, 
iodide and selenide;in combination with silver it occurs 
in the metallic state as an amalgam. 

708. Where is mercury obtained ? 



MEKCUEY. 341 

709. Production. — Mercury is prepared from the 
sulphuret, by simply roasting in a current of heated air. 
This metal yields its sulphur so readily to the oxygen 
of the air that no other agent is essential in its produc- 
tion. The mercurial vapors pass along with the gas, 
into tubes or chambers where the temperature is lower, 
and are there condensed to the liquid form. 

710. Mercury may also be produced from the sulphu- 
ret by the employment of iron filings to remove the 
sulphur, as in the case of lead. Burned lime may also 
be used. Its calcium combines with the sulphur and 
uses its own oxygen for the partial conversion of the 
sulphuret thus formed into sulphate of lime. 

711. Action of Heat and Am. — Mercury, like 
water, may be boiled away and converted into vapor by 
the application of heat. It is always to be borne in 
mind in experiments w T ith this metal and its compounds, 
that its fames as well as its salts are extremely poison- 
ous. By free access of air and moderate heat, mercury 
may be gradually converted into red oxide, but a higher 
temperature expels the oxygen thus absorbed, and the 
oxide is again converted into metal. This production 
of a metal from an oxide, by heat alone, is characteris- 
tic of the noble metals. They are loth to obscure their 
splendor in rust ; if it is forced upon them, they need 
but little assistance of heat to throw it off and re-assume 
their original beauty. 



709. How is mercury obtained? 710. Mention other methods. 711. 
What is the action of heat and air on mercury ? 



342 PRINCIPLES OF CHEMISTRY. 

712. Amalgams. — Glass Mirrors. — Mercury com- 
bines with many metals forming compounds which are 
called amalgams. When the mercury is in large pro- 
portion they are fluid. Gold, silver, and lead, for ex- 
ample, may be dissolved in mercury. This solvent 
power of mercury is usefully applied in extracting gold 
from the rocks which contain it. The gold bearing 
quartz is first crushed in mills and then submitted to 
the action of mercury, which takes up the gold, leaving 
the other materials entirely free from gold. The beau- 
tiful silvering of mirrors consists of an alloy of tin and 
mercury. Tin foil is applied to the glass, and being 
afterward drenched with mercury, the excess is removed 
by pressure. The tin thus absorbs about one-fourth 
of its own weight of mercury. 

713. A copper coin may be similarly silvered by rub- 
bing with metallic mercury, or keeping it well moist- 
ened for some time with a solution of mercury in nitric 
acid. If the solution is quite acid, it must first be 
nearly neutralized by ammonia. The coin is to be 
afterward polished. The chemical action which takes 
place in this case is similar to that explained in the case 
of the lead tree. By drawing a line across a thin brass 
plate with a pen dipped in solution of mercury, the 
plate will be so weakened that it may afterward be 
readily broken. 

714. Other Uses of Mercury. — The compounds of 

712. What are amalgams ? How are mirrors silvered ? 713. How may 
a copper coin be similarly silvered ? 714. Mention some other uses of 
mercury. 



SILVEE. 343 

mercury are extensively used in medicine. Corrosive 
sublimate, a poisonous chloride of mercury, is employed 
for the destruction of vermin. It is also used in what 
is called the kyanizing process, to impregnate wood and 
other vegetable and animal substances, and thus prevent 
their decay. Another important use of mercury is 
found in the manufacture of barometers and thermom- 
eters. It is especially adapted to the measurement of 
heat, by its fluidity at low temperatures and its ready 
and equable expansion. 

Silver. 

Symbol* Ag> (Argentum) ; Equivalent, 108 ; Specific Gravity, 10.5. 

715. Description. — Silver is a lustrous white metal 
of perfect ductility and malleability. Its loss of luster 
on exposure, is owing to the presence of a small pro- 
portion of sulphuretted hydrogen in the air. Nitric 
acid is its proper solvent, though for certain purposes 
oil of vitriol is preferred. Silver is often found native, 
but more frequently combined with sulphur as silver 
glance. Galena or sulphuret of lead always contains 
it in small proportion, and sometimes to the amount of 
one or two per cent. 

716. Production. — Silver is prepared from the sul- 
phuret, by first roasting the ore with common salt, in 
order to convert it into chloride. Iron is subsequently 



715. Silver — description, ores and solvents ? 716. How is silver ob- 
tained ? 



344 PRINCIPLES OF CHEMISTRY. 

employed to remove the chlorine and isolate the metal- 
lic silver. 

717. Mercury is added with the iron, in order that it 
may dissolve the silver from the mass of roasted ore 
and iron as fast as it is formed. The materials are 
agitated with water for many hours together. At the 
end of the process the mercury, with its load of silver, 
is drawn off from the bottom of the cask. The solu- 
tion of silver in mercury is afterward filtered through 
buckskin or closely woven cloth, which allows a large 
part of the liquid metal to pass, while the silver with a 
small portion of mercury is detained. The silver is 
then freed of its remaining mercury by heat. The 
above process is called amalgamation. 

718. Silver obtained from Lead. — Almost all lead, 
as produced from galena and its other ores, contains a 
certain proportion of silver. The latter metal may be 
freed from a large part of the lead by melting the alloy 
and then allowing it to cool slowly. Most of the lead 
solidifies in small crystals, and may be skimmed out 
with an iron cullender. An alloy containing silver in 
large proportion remains in the liquid condition. It 
is afterwards solidified by farther cooling. The above 
is called Pattinson's process. 

719. Cupellation. — The last traces of lead are re- 
moved from silver by a process called cupellation. 
Other base metals are removed in the same manner by 
first adding to the alloy a sufficient amount of lead. 

717. Give the complete process. 718. Describe the process for obtain- 
ing silver from lead. 719. How is silver purified from baser metals ? 



SILYEK. 345 

In case of base metals, other than lead, if the quantity 
contained in the alloy is small, the silver prevents the 
access of air to the baser metal, or an infusible oxide 
forms upon the surface and prevents further oxidation. 
Cupellation depends upon the property which lead 
possesses of absorbing oxygen at a high temperature, 
and of forming with it an easily fusible oxide, which 
imparts oxygen with facility to all those metals which 
yield oxides not reducible by heat alone. Most of 
these oxides thus formed unite with the oxide of lead 
and form a fusible glass which is easily absorbed by a 
porous crucible made 209 210 

of burnt bones termed 
a cupel, figure 209. ^jjf 
Several of these cu- 
pels are placed in a muffle which is a semi-cylindrical 
oven, figure 210, closed at one end and open at the 
other, with slits in the sides to allow the free circulation 
of air. The muffle is placed in a furnace, figure 211, 
fitted with suitable dampers and doors, D, E, F, G, I, 
and L, for regulating the heat to any required temper- 
ature. Fuel is thrown in at B and C, both below and 
above the muffle and a tall chimney, M, secures a suffi- 
cient draft and carries off all the noxious vapors formed. 
After the temperature is raised to bright redness, the 
alloy, if it contains only lead, is placed in one of the 
cupels. If it contains some other metal it is first 
laminated and wrapped in a suitable quantity of pure 
sheet lead and placed in the cupel. The metals soon 
melt and by the action of air which plays over the hot 




346 



PRINCIPLES OF CHEMISTRY. 



surface the lead and other base metal, if any, are oxidized, 
and the fused oxides are absorbed by the porous cupel. 




If the operation has been skillfully conducted a button 
of pure silver alone remains. The silver does not oxi- 
dize under these circumstances, but retains the metallic 
form. The mass of metal grows smaller as the process 
proceeds, until finally pure silver remains. The mo- 
ment of its production is indicated by a beautiful play 
of colors and a sudden brightening of the metal. The 
refiner watches this process and when the globule of 
melted metal appears like a brilliant mirror he knows 
that the process is completed. The metal is then al- 
lowed to cool very gradually. 




SILVER. 347 

720. This process may be illustrated on a small scale, 
by making an excavation in a piece of charcoal, and 
pressing into it a lining of well 212 
burned and moistened bone ash. A 
globule of lead, to which a little sil- 
ver has been added, is to be heated 
on the support in the oxidizing flame. 

For separating a small quantity of lead from silver, the 
bone ash is not essential. The process may be con- 
ducted before the blowpipe, upon the naked charcoal. 
A small portion of silver may often be obtained from 
the lead of commerce by this means. 

721. Silver Coin. — The standard silver of the Uni- 
ted States is an alloy containing ten per cent, of cop- 
per. Silver plate should have the same composition. 
The object of alloying with copper is to impart greater 
hardness to the metal, and secure against the gradual 
loss from attrition which would otherwise occur. Span- 
ish silver often contains a small proportion of gold. 
The gold is left as a black powder, in dissolving such 
coins in nitric acid. Its color and luster may be brought 
out by rubbing. 

722. The Silver Assay. — Assaying is the process 
by which the proportion of metals in an alloy is ascer- 
tained. In all establishments where money is coined, 
assaying is an important part of the work of the estab- 
lishment. The precious metals, as received at the mint, 
commonly contain a certain proportion of other metals. 

720. How may the process be iUustrated ? 721. What is said of silver 
coins ? 722. What is assaying, and why necessary ? 



348 



PRINCIPLES OF CHEMISTRY. 



213 



But it may be too much or too little. It is tlie business 
of the assayer to ascertain its precise composition, that 
the metal may be rendered purer, if necessary, or be 
further alloyed if found purer than the standard. 

723. As a preparation for the silver assay, a sample, 
containing an ounce or other definite weight of the im- 
pure metal, is dissolved in nitric acid. The dissolved 

silver has the property of becoming solid 
again, and sinking to the bottom of the 
clear solution as a white curd, just in pro- 
portion as common salt is furnished to it. 
But the other metals which may be present 
as impurities have no such effect. It fol- 
lows, that the amount of silver present, is 
just in proportion to the amount of salt it 
is necessary to supply before the precipitation or for- 
mation of the curd ceases. Bow, the assayer knows 
beforehand, how much salt he must supply to the solu- 
tion of an ounce of metal if it be all silver. If he 
finds that an ounce of the sample, requires to be sup- 
plied with the same quantity before the precipitation 
ceases, he knows that the metal is all silver ; if but half 
as much is required, he knows that it is but half silver. 
Having ascertained the true proportion, the assay is 
completed. The salt required in the process is em- 
ployed in the form of a solution, and the quantity used 
is known by pouring it from a graduated vessel. 

724. Explanation. — The curd which forms in the 




723. Describe the process of assaying. 724. Explain the chemical 
action in the above process. 



SILVER. 349 

above process is insoluble chloride of silver, formed 
from the silver of the solution and the chlorine of the 
salt. The nitric acid and oxygen, which were com- 
bined with the silver, at the same time unite with the 
sodium, forming nitrate of soda which remains in solu- 
tion. 

725. Silver separated from Copper. — Copper ob- 
tained from certain ores contains so much silver as to 
make its separation an object of importance. The 
method pursued is to fuse the copper with lead. As 
the lead flows out again by subsequent fusion, it brings 
with it all the silver, and the copper remains behind as 
a spongy mass. This process is called liquation. The 
silver is then freed from lead by the process of cupella- 
tion already described. 

726. Uses of Silver. — Most uses of silver are so 
familiar that they need not be here mentioned. Its 
employment for daguerreotype plates depends on the 
fact that the color of many of its compounds is readily 
changed by light. This subject is more fully consid- 
ered in the section on Chlorides. The nitrate of silver 
or lunar caustic, is used in surgical operations, to burn 
or cauterize the flesh. In solution, it is also employed 
as a hair dye, and in the production of indelible ink. 



725. Describe the method of extracting silver from copper. 726. 
Mention some uses of silver. 



350 PRINCIPLES OF CHEMISTRY. 

Gold. 

Symbol, Au. (Aurum) ; Equivalent, 191 ; Specific Gravity, 19.3. 

727. Description. — Gold is a yellow metal of brill- 
iant and permanent luster. Its extreme malleability is 
strikingly illustrated by the fact that it may be ham- 
mered into a leaf but a little more than 3 o o?o oo of an 
inch in thickness. As the fact may be otherwise stated, 
a cube of gold five inches on a side could be so extend- 
ed as to cover more than an acre of ground. Such gold 
leaf is permeable to hydrogen. A jet of this gas may 
be blown through it and kindled on the opposite side. 
Gold is proof against all ordinary acids excepting aqua- 
regia. It is found only in the metallic state, and com- 
monly either in quartz rock or in the sands of rivers. 
Native gold contains from five to fifteen per cent, of 
silver. 

728. Production. — The Refining Process. — Native 
gold may be freed from the silver which it contains, by 
the agency of concentrated sulphuric or nitric acid. A 
difficulty in accomplishing this result arises from the 
fact that every particle of silver is so perfectly sur- 
rounded by gold, that the acid does not readily reach 
it. This difficulty is overcome by fusing more silver 
into the gold, and thus opening a passage for the sol- 
vent. This being done, both the original silver and 
that which has been added are readily removed. The 

727. Mention some properties of gold. Its solvent, and occurrence. 
728. How is pure gold produced ? 



GOLD. 351 

above is the process at present pursued in France for 
refining gold. 

729. Axother Method. — The second method is essen- 
tially the same as that already described, with the sub- 
stitution of nitric for sulphuric acid. The addition of 
silver, as a preliminary step, is found necessary in this 
process also. So much silver is added, that the gold 
forms but a quarter of the mass exposed to the action 
of the acid. The method is hence called quartation* 
The process involves a previous knowledge of the 
approximate composition of the mixed metal. This 
may be obtained by the touchstone, as hereafter de- 
scribed. 

730. Amalgamation. — Gold may be obtained from 
any material which contains it, even in small propor- 
tion, by the process of amalgamation. This process 
consists in agitating the finely divided material with 
mercury, until the latter has extracted all of the preci- 
ous metals. It is then obtained from its solution in 
mercury by the same means employed in the case of 
silver. This method is adopted in the case of the gold- 
bearing quartz of California. The dust of jewelers 
shops is similarly treated in order to save the small 
proportions of gold which it contains. 

731. Gold from Lead and Copper. — Certain ores 

729. Describe another method. 730. What is amalgamation? 731. 
How is gold separated from lead and copper ? 



* In the practice of the United States Mint, the addition of less silver has been 
found sufficient. The proportion of gold is there increased to one-third. Nitric acid 
is then employed in the refining process. 



352 PRINCIPLES OF CHEMISTRY. 

of lead and copper contain so much gold that it is 
profitable to extract it from the metal which they yield. 
This is done by the processes of liquation and ctcpetta- 
tion before described. 

732. Gold from Sulphurets of Iron, &c. — Sulphu- 
rets of iron, copper, &c, sometimes contain gold, in 
small quantity, and so completely disseminated that it 
cannot be readily extracted by mercury. It has been 
found advantageous to heat such ores with nitrate of 
soda, previous to amalgamation. The sulphurets are 
thus partially converted into sulphates, which can be 
washed out. What remains of the pulverized material 
is at the same time thoroughly opened to the action of 
mercury. 

733. The Gold Assay. — Gold to be assayed con- 
tains commonly only silver and copper as impurities. 
By fusing the sample with lead and then removing this 
metal by cupellation, it carries with it the copper, into 
the cupel. A globule containing only gold and silver 
remains. The silver is then dissolved out by nitric 
acid. The remaining sponge of pure gold being 
weighed, and its weight compared with that of the 
original sample, the assay is completed. More silver 
is added in the process, for reasons stated in a previous 
paragraph. 

734. Assay of Gold by the Touchstone. — Any 
hard and somewhat gritty stone of a dark color which 

732. How is gold obtained from certain sulphurets ? 733. Describe the 
method of assaying gold ? Why is silver added ? 734. What is the 
touchstone and how is it used in assaying gold ? 



GOLD. 353 

is not acted on by acids answers the purpose of a touch- 
stone, The assay consists in marking upon the stone 
with the alloy, and judging of the purity of the metal 
from the color of the mark, and the degree in which it 
is affected by an acid. Citric acid, to which a very 
small quantity of muriatic acid has been added, is em- 
ployed in this test. Gold alone is proof against its 
action. In proportion to the permanence of the mark, 
is the purity of the gold which has been submitted to 
the assay. 

735. Gold Coin. — The gold employea for coin, plate 
and jewelry is always alloyed with a certain portion of 
copper or silver, to give it greater hardness. The 
standard gold of the United States is nine-tenths pure 
gold, the remaining tenth being an alloy of copper and 
silver. 

736. Purity or Gold. — The purity of gold is ex- 
pressed in carats, a carat signifying, practically, one 
twenty-fourth. Thus, when gold is said to be sixteen 
carats fine, it is meant that two-thirds of it is pure gold. 
Gold eighteen carats fine is three-fourths pure gold and 
one-fourth alloy. 

737. Gilding. — Gilding by the Yoltaic battery has 
been already described. This method is, in most cases, 
preferable to all others. Copper jewelry is thinly 
gilded by boiling in a solution of gold in carbonate of 
soda or potash. The solution is prepared by first dis- 
solving the gold in aqua regia, and afterward precipi- 

735. WTiat is said of gold coin ? 736. How is the degree of purity of 
gold expressed ? 737. How is copper jewelry gilded ? 



354 PRINCIPLES OF CHEMISTRY. 

tating and re-dissolving it by means of the carbonate 
above named. 

738. Gilding may also be effected by an amalgam of 
gold and mercury. The amalgam being applied, the 
mercury is expelled by heat and the gold remains. 
This method is very frequently employed. A coating 
of pure gold is produced upon articles of jewelry, made 
of impure metal, by first heating them, and then dis- 
solving out the copper by means of nitric acid. 



Platinum. 

Symbol, Pt; Equivalent, 99 ; Specific Gravity, 21.5. 

739. Description. — Platinum is the last of the noble 
metals. It resembles steel in color, and possesses a 
high degree of malleability. It is the heaviest and 
the most infusible of all metals. At a white heat it 
may be welded like iron. Like gold it resists the action 
of any single acid, but may be dissolved in aqua regia. 
It is commonly found, like gold, in small flattened 
grains in the alluvial strata and rivers of Brazil, Peru 
and Mexico, and in the Uralian mountains of Siberia. 
It has also been found in California and Australia. 
Rounded masses of the metal are sometimes found as 
large as a pea or a small marble, and some have been 
found as large as a pigeon's egg. These grains usually 
contain also gold, iron, lead, and some other rare metals, 

738. Describe the method of gilding by an amalgam. 739. Platinum—, 
description, occurrence, solvents ? 



PLATINUM. 



355 



as palladium, rhodium, iridium and osmium, which are 
of little interest except to the professional chemist. 
The value of platinum is about one-half that of gold. 

740. Preparation. — The usual method of obtaining 
pure platinum is to digest the ore in nitrohydrochloric 
acid, decant the clear solution from the black insoluble 
residue and mix it with a solution of sal- 214 
ammoniac ; a yellow double chloride of 
ammonium and platinum falls, which 
when well washed and heated to redness 
leaves a spongy mass of finely divided 
metallic platinum. The spongy platinum 
is triturated with water and then con- 
densed in a steel mold, figure 214, until 
it is sufficiently compact to bear the blows 
of a hammer ; it is then heated and forged 
until perfectly tough and homogenous. 

741. .Deville and Debeay's Method 
of Preparing Platinum. — The prepared 
ore is fused with its weight of sulphuret of lead and 
half its weight of metallic lead ; some of the impurities 
are thus separated in combination with sulphur, while 
the platinum forms an alloy with the lead, which is 
freed from the scoriae, and subjected to the joint action 
of heat and air, until the greater part of the lead is 
oxidized into litharge, so that the residuary alloy only 
retains about 5 per cent, of lead. It is then subjected 
to the intense heat of an oxyhydrogen flame in a furnace 



740. How is pure platinum prepared ? 741. Describe Deville and De- 
bray's method 01 preparing platinum. 



356 



PRINCIPLES OF CHEMISTRY. 



of chalk-lime, figure 215, where the rest of the lead, 
(together with any gold, copper and osmium), is driven 

off in fumes ; the remain- 
ing platinum is cast into 
any required form. 

742. The Oxyhydro- 
gest Furnace shown in 
section at figure 215, 
consists of three pieces 
of well burnt lime of 
slightly hydraulic quality 
which can readily be 
turned in a lathe. The 
cylinder A A is about 
2^ inches thick and is 
perforated with a slightly 
conical tube into which 
the tube of the oxyhydro- 
gen blow-pipe is inserted, passing about half way through 
it ; a second deeper cylinder of lime, B B, is hollowed 
into a chamber wide enough to admit the crucible and 
leaVe an interval of not more than a sixth of an inch 
clear around it. At K K are four apertures for the 
escape of the products of combustion. A crucible, I, 
with a conical cover, G, is enclosed in a crucible, H H, 
made of lime. The coke crucible standing upon a 
lime support, D, contains the substance to be melted 
and it is so placed that the apex of the cover is exactly 
under the blow-pipe jet at a distance from £ to 1^ inch 

742. Describe the oxyhydrogen furnace for melting platinum. 




PLATINUM. 357 

from it. At the International Exhibition of 1862, 
Messrs. Johnson exhibited a mass of pure platinum 
(prepared by Deville's process in a furnace of this kind,) 
weighing 230 pounds and valued at 3840 pounds ster- 
ling, equal to about seventeen thousand dollars. It thus 
appears that the great problem of melting large masses 
of platinum, hitherto considered almost an impossibility, 
has been completely solved. 

743. Platinum condenses Gases — The metal plati- 
num has the remarkable property of condensing gases 
upon its surface, and thereby increasing their affinities. 
This effect is in proportion to the surface 
exposed. It may be prepared for this ex- 
periment by burning paper, previously mois- 
tened with a solution of this metal. Such 
an ash, by simple exposure to the air, con- 
denses and retains a large quantity of oxy- 
gen within its pores. On holding it in a jet 
of hydrogen, the condensed oxygen imme- 
ately unites with the latter gas so energetically as to 
inflame it. 

744. Platinum is employed for similar purposes, in 
the form of a sponge, and as a powder, called platinum 
Hack. A mixture of nitric oxide and hydrogen, passed 
through a tube containing heated platinum black, issues 
from the tube as ammonia and water. The hydrogen 
has entered into combination with both of the elements 
of the nitric oxide, producing two new compounds. 

743. Mention a remarkable effect of platinum on gases. 744. Give 
another illustration of this effect. 




35S PRINCIPLES OF CHEMISTRY. 

745. Other Uses of Platinum. — The most impor- 
tant use to which platinum is applied in the arts, is in 
the manufacture of chemical apparatus. Its extreme 
infusibility and resistance to acids, adapt it especially 
to this purpose. In the manufacture of oil of vitriol, 
for example, no other material excepting gold could 
well take the place of the platinum vessels in which 
concentration is effected. Platinum crucibles are also 
invaluable, as they may be exposed to the fire of a blast 
furnace without injury. Nothing less than the most 
intense heat of the oxyhydrogen blow-pipe, or Galvanic 
battery, is sufficient to fuse this metal. 

Alloys. 

746. Alloys are compounds of the metals with each 
other. Comparatively few of the metals possess such 
qualities as render them suitable to be employed alone 
by the manufacturer; zinc, iron, tin, copper, lead, 
mercury, silver, gold and platinum are all that are so 
used. Antimony, arsenic and bismuth are too brittle 
to be used alone but are very useful for hardening other 
metals. By combining two or more metals their prop- 
erties are so altered that the compound is adapted to 
many valuable purposes for which neither metal could 
be used alone. Antimony is too brittle for type-metal, 
and lead is so soft it would soon be crushed under the 
press, but four parts lead and one of antimony give an 

745. Why is platinum superior to other metals for chemical apparatus ? 
746. What are alloys ? How are the properties of metals affected by 
combination ? 



ALLOYS. 359 

alloy that will sustain the requisite pressure without 
crushing or cracking. Brass, an alloy of copper and 
zinc, is harder and more easily wrought than copper 
and far more tenacious than zinc. The chemical prop- 
erties of alloys are generally such as might have been 
anticipated from the nature of the components. Yet 
the alloy of two oxidizable metals is sometimes more 
readily oxidized than either of the components. The 
melting point of an alloy is generally lower than the 
mean of the metals which compose it. The ductility 
of metals is also generally impaired by combination 
with one another. 

747. Alloys used ts the Manufactures. — Brass 
is an alloy of copper with about one-half its weight of 
zinc, but the proportions are varied to suit different 
purposes : Lead and tin are sometimes added. 

Muntzh Patent Sheathing Metal. A good substitute 
for copper — contains three-fifths copper and two-fifths 
zinc. 

Speculum Metal contains about 6 parts of copper, 2 
of tin and 1 part of arsenic. Lord Eosse employed for 
the speculum of his great telescope an alloy of about 
682 parts copper to 318 parts of tin. 

German Silver is an alloy of 100 parts copper, 60 
of zinc and 40 of nickel. The white color is due to 
nickel. An alloy of 30 parts silver, 25 of nickel, and 
55 of copper, forms a nearly perfect substitute for silver 
for all ornamental purposes. 

747. What alloys are in common use ? What is their composition ? 



360 PRINCIPLES OF CHEMISTRY. 

Bronze is copper containing ten per cent, of tin. 
Tempering produces upon bronze an effect directly- 
opposite to that upon steel; and in order to render 
bronze malleable it must be heated to redness and 
quenched in water. The alloy which thus acquires 
the greatest tenacity contains 8 parts of copper to 
1 part tin. This alloy is particularly suitable for 
medals. It suffers less than copper by friction and 
oxidation. 

Bell metal is a kind of bronze containing copper 78, 
and tin 22 parts in 100. 

Pewter is an alloy of tin with variable proportions 
of antimony or lead. Britannia ware, so called, is a 
sort of pewter. 

Type-metal is an alloy of lead with about one-fourth 
its weight of antimony. By the use of tin, instead of 
lead, a better, but more expensive type-metal may be 
produced. Zinc, with a few per cent, of copper, lead, 
and tin, have also been recently employed. Type-metal 
is sufficiently fusible to allow of its being readily cast ; 
it expands at the moment of solidification and copies 
the mold accurately. It is hard enough to bear the 
action of the press, and yet not so hard as to cut the 
paper. 

Fine and coarse solders are alloys of tin and lead, the 
former being two-thirds and the latter one-fourth, tin. 
Hard solder is a variety of brass. 

JVewton's Fusible Metal, which has the remarkable 
property of melting in boiling water, is composed of 8 



ALLOYS. 361 

parts of bismuth, 5 of lead, and 3 of tin. An alloy of 
2 parts bismuth with one of lead and one part tin melts 
at 201° Fahrenheit. 

Wood's Fusible Metal consists of cadmium 1 part, 
tin 1, lead 2 and bismuth 4 parts. It melts at about 
150° F. By varying the proportions the melting point 
may also be varied. Its fusing point may be lowered 
to any extent by the addition of mercury, which may 
be employed within certain limits without materially 
impairing the tenacity of the metal. Another alloy 
devised by Mr. Wood, containing cadmium 1 part, 
lead 6, and bismuth 7 parts, melts at 180° Fahrenheit. 
It takes less cadmium to reduce the melting point of an 
alloy a certain number of degrees than it requires of 
bismuth, besides that the cadmium does not impair the 
tenacity and malleability of the alloy, but increases its 
hardness and general strength. 

Alloys of Aluminum. Aluminum forms several 
alloys of much value in the arts. An alloy of 1 part 
silver with 20 parts of aluminum works like silver, but 
is harder and takes a finer polish. One-twentieth part 
of aluminum gives to copper a beautiful gold color and 
hardness enough to scratch the standard alloy of gold 
used for coins, but the malleability of the alloy is much 
less than of copper. One-tenth of aluminum gives 
with copper a pale gold-colored alloy of great hardness 
and malleability, and capable of taking a polish like 
that of steel. One part of aluminum with 20 parts of 
pure silver gives an alloy almost as hard as silver coin 
containing one-tenth of copper, and thus permits us to 



862 PRINCIPLES OF CHEMISTRY. 

harden silver without introducing a poisonous metal. 
Many of the above alloys are slightly varied in their 
character by the addition of other metals in small 
quantity. 



CHAPTER III. 

SALTS. 

SOLUTION AND CRYSTALLIZATION. 

748. Definition. — Under the general head of salts, 
are included all compounds of acids and bases, and be- 
side these, the compounds of chlorine, bromine, iodine, 
sulphur, &c, with the metals. Sulphate of copper or 
blue vitriol is an example of the first class, and chloride 
of sodium, or common salt, of the latter. 

749. Neutral, Acid and Basic Salts. — In general, 
salts containing an equivalent of base to an equivalent 
of acid are called neutral. The composition fixes the 
name, whether exactly neutral to the taste and in their 
action on vegetable colors, or not. Salts containing 
more acid in proportion are called super-salts or acid 
salts, and those containing more base, sub-salts or basic 
salts. 



748. What compounds are called salts ? 749. What are neutral, acid, 
and basic salts ? 



SALTS. 363 

750. There are two exceptions to the above rules. The 
first is that of certain classes of acids which have double 
and treble neutralizing power, and require therefore, the 
first two atoms and the latter three atoms of base, to 
make them neutral salts. Such acids are bibasic and 
tribasic, in contradistinction from the monobasic or 
ordinary acids. Phosphoric acid is one of the latter 
class of tribasic acids, and the neutral phosphates 
have therefore three atoms of base and are called tri- 
basic phosphates. Phosphates containing more acid 
or base than their proportion are acid or basic accord- 
ingly. The second exception is that of salts or bases 
which contain more than one atom of oxygen to an 
atom of metal. In proportion as they contain more, 
they neutralize more acid. Alumina or oxide of 
aluminum, for example, contains three atoms of oxy- 
gen, (A1 2 3 ). Its neutral sulphate, therefore, is a salt 
containing 3 atoms of acid as sulphate of alumina, 
(A1 2 3 ,3S0 3 ). A salt of alumina containing more 
or less than this proportion, is acid or basic accord- 
ingly. 

751. Double Salts. — There are also double salts or 
compounds of salts with each other. They are gener- 
ally of the same acid. Thus alum (K0,S0 8 ,A1 2 3 ,3S03 
+ 24 HO), is a double sulphate of potassa and alumina, 
and the bisulphate of potassa (§ 766) may be regarded 
as a double sulphate of potassa and water. Such double 
salts are not mere mixtures. They have their own 



750. What exceptions are mentioned? 751. What are double salts? 



364 PRINCIPLES OF CHEMISTRY. 

crystalline form, and each molecule of their crystals 
contains all the elements of both salts. 

752. Binary Theory of Salts. — Sulphate of potas- 
sa, and other similar salts, are commonly regarded as 
ternary compounds. But many chemists are of the 
opinion that they are constituted after the plan of the 
binary salts, and their acids on the plan of a hydrogen 
acid. They would write sulphuric acid, S0 4 H, instead 
of HO,S0 3 , thus indicating that the hydrated acid is 
composed of the radical, S0 4 , (a compound playing the 
part of an element,) with hydrogen* Sulphate of 
potassa would, according to this view, be written K, 
S0 4 , instead of KO,S0 3 . The acid and salt are thus 
represented as analogous in constitution to a hydracid 
and a binary salt ; thus, (S0 4 )H corresponds with C1H, 
and (KSO4) with KC1. The advantage of this view is 
that it makes but one great class of acids and one of 
salts, associating substances which are analogous in 
their properties. Hydrogen thus becomes characteristic 
of an acid. 

This view also simplifies the subject of the produc- 
tion of salts from acids, making it to consist simply 
in the replacement of the hydrogen of the acid by 
a metal. Thus in the action of sulphuric acid (HO, 
S0 3 ) on zinc, sulphate of zinc (ZnO,S0 3 ) is formed by 
the simple replacement of the hydrogen of the acid by 
the metal zinc. As will be seen more clearly in the 
introduction to Organic Chemistry, it is no conclusive 

752. What is said of the binary theory of salts 



SALTS. 365 

objection against this view, that the radical S0 4 has not 
been isolated. There is the best reason for believing in 
the existence of many such hypothetical radicals. A 
similar objection has indeed been urged against the 
ordinary view, according to which S0 3 neutralizes 
potassa in the sulphate of this base. The objection lies 
in the fact that anhydrous sulphuric acid is not pos- 
sessed of acid properties, and can therefore be scarcely 
regarded as an acid, in its anhydrous condition. 

753. Preparation of Salts. — The salts of most acids 
may be produced by simply bringing the acid and oxide 
together. Sulphate of potassa is thus produced from 
sulphuric acid and potassa. Heat is sometimes required 
to bring about the combination. They may also be 
prepared from the carbonates. Thus, acetate of lime 
is produced by pouring strong vinegar on chalk, or car- 
bonate of lime. Carbonic acid is in such cases expelled 
by the stronger acid which is employed. Other 
methods of preparing individual salts will be here- 
after given. 

754. Solution. — The particles of all bodies are held 
together, as before explained, by the attraction of co- 
hesion. But water has also an attraction for these 
particles. In the case of many substances, it over- 
comes the force of cohesion and distributes them 
throughout its own volume. Such a distribution, in 
which the solid form of the solid is entirely lost, is 
called solution. Different liquids are employed as sol- 

753. Mention some methods of preparing salts ? 754. Explain solu- 
tion. 



366 PRINCIPLES OF CHEMISTRY. 

vents for different substances. A solution is said to be 
saturated when no more of the solid will dissolve in it. 

755. Precipitation. — In solution, the particles of 
bodies have not lost their property of cohesive attrac- 
tion. It is only overcome by a superior force. As 
soon as this is weakened they unite again to form a 
solid. The solvent power of alcohol for camphor, is 
thus diminished when water is added to the solution. 
As a consequence, the camphor immediately reassumes 

the solid form. This experiment is made 
by adding water to an ordinary solution 
of camphor. "When a solid is thus re- 
produced from a liquid, it is called & precipi- 
tate. 

One case of precipitation has been already 
mentioned. But it may be effected by various methods. 
All of these may be arranged under two heads ; pre- 
cipitation by changing the character or quantity of 
the solvent, and precipitation by changing the' substance 
dissolved. 

756. Change of Solvent. — The three cases in which 
precipitation is effected by changes in the solvent, are, 
mixing, cooling, and evaporation. The first has just 
been described. The second is illustrated in the pro- 
duction of alum crystals by cooling a hot solution. The 
third consists in dissolving a solid in some liquid and then 
boiling away the latter. The experiment may be tried 



755. Have the particles lost their cohesive attraction ? how may they 
be precipitated Mention two general methods of precipitation. 756. 
Mention three cases of precipitation by change of solvents. 




SALTS. 367 

with a saturated solution of salt and water. As fast 
as the water is boiled away, the portion which has lost 
its solvent re-assumes the solid form. 

757. Change of Substance dissolved. — The change 
in the substance dissolved, is effected in some cases by 
addition, and in others by subtraction. Carbonic acid 
blown through lime water precipitates it by addition. 
The precipitate is chalk or carbonate of lime. Potash 
added to a solution of sulphate of copper, precipitates 
it by substraction ; the precipitate is oxide of copper, 
deprived of its acid by the potash. 

758. Explanation. — The above cases of precipitation 
demand some further explanation. As fast as carbonic 
acid is blown into the lime water, in the first case, the 
new substance, chalk or carbonate of lime, is produced 
throughout the liquid. TYe may suppose that innume- 
rable particles are first formed, before they unite to 
form a precipitate. But the cohesive attraction put 
forth by the particles of this new compound is so great 
that the opposing attraction of the water is overcome, 
they rush together, and assume the solid form of a pre- 
cipitate. This did not happen in the case of lime alone, 
because the cohesive attraction between its particles is 
inferior to the opposing attraction of the water. The 
second case is to be similarly explained. 

759. Relation of Cohesion and Affinity. — The 
chemical affinity of potassa for carbonic acid is evi- 



757. Describe two cases by change of substance. 758. State the cause 
of precipitation in the above cases. 759. What is said of the relation of 
cohesion and affinity ? 



368 PRINCIPLES OF CHEMISTRY. 

dently greater than that of lime. The former base re- 
tains the acids so firmly that no degree of heat can 
effect it, while the latter gives up its acid with readi- 
ness, under the influence of a high temperature. Not- 
withstanding the superior affinity of potassa, lime will 
take from it its carbonic acid, if added to a solution of 
carbonate of potassa in water. The mixture being 
made, the particles in this and in all similar cases tend 
to re-arrange themselves in the solid form. They seem 
to do this without reference to their chemical affinities, 
in such a manner as best to resist the solvent action of 
the water or other liquid. Carbonate of lime resists 
such action better than carbonate of potassa. The for- 
mer is therefore produced. The cohesion of carbonate 
of lime, using the term in the sense of capacity to re- 
sist the separating power of water, has therefore de- 
termined the production of this substance in opposition 
to ordinary chemical affinities. 

760. The above case illustrates a general law. Two 
substances, which when united form an insoluble com- 
pound, generally unite and produce it, when they meet 
in solution. To illustrate by another example : phos- 
phate of lime or bone ash is insoluble. Then we may 
be sure that phosphoric acid and lime, if brought to- 
gether by mixing two solutions, will desert any sub- 
stances with which they were before combined, and 
unite to form insoluble phosphate of lime. This rule 
is not without exceptions, but it enables the chemist to 

760. State and illustrate the general law. 



SALTS. 369 

determine beforehand innumerable cases of precipita- 
tion. 

761. Solution and Chemical Combination. — Solu- 
tion differs from chemical combination in the varying 
proportions in which it occurs according to temperature 
and in the absence of any change of chemical proper- 
ties. Nitre, for example, dissolves in water at 100°, in 
nearly double the quantity which will dissolve at 70°. 
At the same time, it forms a solution to which it has 
imparted its own chemical properties unchanged. 

762. Another important distinction is found in the 
following fact. While chemical combination is most 
active between bodies whose properties are most op- 
posed, such as acids and bases, solution occurs most 
readily in the case of similar substances. The metals 
dissolve in mercury. Salts dissolve in water. Fats and 
resins dissolve in alcohol and ether, which, like them- 
selves, contain much hydrogen. 

763. Crystallization. — In passing from the liquid to 
the solid condition, the particles of most bodies assume 
a crystalline arrangement. *Their mutual attraction is 
more than a mere force which draws and binds them 
together. It groups them in regular forms. The crys- 
tals thus produced are often too small to be separately 
seen. But even where this is the case, the crystalline 
structure is readily observed. Surfaces of zinc or cast 
iron exposed by recent fracture, are familiar examples. 



761. How does solution differ from chemical combination ? 762. State 
another important distinction. 763. What is said of crystaUine arrange- 
ment ? 



370 PRINCIPLES OF CHEMISTRY. 

But where the circumstances are favorable for the for- 
mation of individual and separate crystals, the most 
beautiful and symmetrical forms are often the result. 

764. Production of Crystals. — Most of the 

218 

salts to be described in this chapter may be ob- 
tained in the form of crystals by evaporating or 
cooling their saturated solutions. The method 
by cooling has already been described in the 
chapter on "Water. In obtaining crystals by 
evaporation, the solution is to be moderately 
heated in a saucer or other vessel. 

765. Water of Crystallization. — The crys- 
tals formed by either method commonly contain water, 
which becomes part of the solid crystal, and is called 
water of crystallization, the amount of which often 
depends upon the method of forming the crystals. 
Salts containing water in a state of combination are 
called hydrated salts. Sulphate of magnesia (epsom 
salts) when crystallized by evaporation at common 
temperatures contains seven atoms of water to each 
atom of salt ; if crystallized by evaporation at a high 
temperature the crystals contain six atoms of water, 
and if crystallized from solutions below 32° large crys- 
tals are obtained containing twelve atoms of water to 
one atom of the salt. Some crystalline salts contain 
no combined water, and are hence called anhydrous 
salts. If Epsom salt, sulphate of magnesia, is heated 
to 125° the salt retains only six equivalents of water ; 

764. How may crystals be produced ? 765. What is water of crystal- 
lization ? ^u 



SALTS. 371 

at a temperature of nearly 300° but one equivalent of 
water is retained, yet this one atom of water is retained 
even at a temperature of 400°. When common alum 
is heated it is dissolved in its own water of crystalliza- 
tion, which amounts to 45 per cent, of its own weight. 
"When the water is all expelled an anhydrous insoluble 
powder remains. 

766. Basic "Water isr Salts. — In some crystals a 
part of the water cannot be removed without entirely 
decomposing the salt. Water thus combined, forming 
an essential part of the salt, is called basic water. Or- 
dinary sulphate of potash contains one equivalent of 
potash combined with one equivalent of sulphuric acid. 
Its composition is expressed by the formula KO,S0 3 , 
the comma after KO (oxide of potassium) indicating 
that it is chemically united with the sulphuric acid 
represented by S0 3 . There is another salt called the 
bisulphate of potash which, contains two equivalents of 
sulphuric acid to one equivalent of potash, but it also 
contains one equivalent of water so closely combined 
with it that it cannot be removed without removing a 
part of the sulphuric acid. The formula for this salt is 
KO,HO,2S0 3 . Here the water, HO, acts the part of 
a base and is hence called basic water, because one 
atom of potash, KO, and one atom of water, HO, 
neutralize two atoms of sulphuric acid expressed by 
the symbol 2S0 3 . Oxalic acid forms two salts with 
potash one of which is represented by the formula 

766. What is basic water ? 



372 



PRINCIPLES OF CHEMISTRY. 



(2KO,C 4 6 + 2Aq), and the other by the formula (KO, 
HO,C 4 6 + 2 Aq). In these formulas 2 Aq represents two 
atoms of water ( Aqua) of crystallization. The symbol is 
preceded by the sign of addition, + , to show that the 
water is added to the salt but not chemically combined 
with it, but the atom of water represented in these 
formulas by HO preceded by a comma is considered as 
an essential part of the salt for it cannot be removed 
without removing at the same time a part of the acid. 
This atom of HO is called basic water while that which 
is represented by Aq is water of crystallization. 

767. Yariety of Crystals. — The forms of leaves 
and flowers are scarcely more various than those of 
crystals. The latter are, as it were, the flowers of the 
mineral world, as distinctly characterized in their pecu- 
liar beauty as the flowers that bloom in the air above 
them. Even where color fails, the eye of science dis- 
tinguishes peculiar features which often enable it to 
determine the nature of a substance from the external 
crystalline form which it assumes. 

219 220 221 222 223 





768. Forms of Crystals. — As every flower has its 
own distinctive form of leaves and petals, so every sub- 



767. How may the variety of crystals be illustrated ? 768. What is 
said of the variety of forms in a single substance ? 



CRYSTALS. 373 

stance has its own form or set of forms from which it 
never essentially varies. Among these or its combina- 
tions, it is, as it were, left free to choose in every crys- 
tal which it builds. The mineral quartz, which caps 
its prismatic palace with a hexagonal pyramid, is an 
example. Its common form represented in figures 14A 
and 222 is a combination of the prism and double six- 
sided pyramid, which commence the series. 

769. A form similar to the double six-sided pyramid, 
with faces corresponding to its twelve converging edges, 
belongs to the same set. Double pyramids similar to 
each of these, but of one-half or one-third their relative 
height, or differing from them by some other simple 
ratio, also belong to the same set of forms. Figure 221 
represents a form composed of two of these pyramids. 
Figure 223 represents another form in which one of 
them is modified by two faces of a prism. To all of 
these and certain other intimately related forms, the 
imaginary privilege of selection and combination, above 
referred to, extends. But most substances, like quartz, 
as above described, affect some particular shape or com- 
bination in which they usually appear. 

770. Modifications of Crystals. — "Whatever the 
form or combination may be, it is susceptible of varia- 
tion, in any degree, so long as its angles correspond to 
those of the perfect shape. Thus the mineral quartz, 
in its commonly occuring combination, is not restricted 
to a perfectly symmetrical shape, like that above pre- 

769. Describe some forms ot a single set. 770. What modifications of 
the same form may occur ? 



374 



PRINCIPLES OF CHEMISTRY 




sented. It may develop one surface and diminish the 
others to any extent. Forms such as are represented in 

the margin result. Differ- 
ent as they seem, it will be 
observed that they agree 
precisely with the perfect 
shape in the angles between 
the surfaces of the prism 
and pyramid, and the different surfaces of each. In 
this their identity as crystalline forms consists. It 
would thus seem that nature pays exclusive attention to 
the corners and angles in her various systems of crys- 
talline architecture. 

771. The least variation of the relative length of the 
vertical axis that is not by some simple ratio, constitutes 
a new and distinct form. This has its related forms as 
before, the whole making a new and distinct set, to 
which the choice of any substance that enters it is 
limited. 

772. Systems of Crystal Forms. — It will be obvi- 
ous to the student that the substitution of 
an octahedron, such as is represented in the 
accompanying figure, for the double six-sided 
pyramid, would be the starting point of an 
entirely distinct system of forms. Within 

its limits there might be innumerable sets as before. It 
would be, as it were, the type of a new order of crys- 



227 




771. What constitutes a new set ? 772. Define another system of crys- 
talline forms. 



CRYSTALS. 



375 



talline architecture, susceptible of variations consistent 
with the general style. 

773. A third system is characterized by inequality in 
three principal dimensions. The axes or lines connect- 
ing the solid angles in the octahedron, and joining the 
'faces in the prism, are all unequal. As each axis may 
be indefinitely varied in this system, there is room 
within its limits for still greater variety than before. 
The fourth system differs from the third in an oblique 
position of some one of the unequal axes. The student 
will readily imagine certain oblique forms which it in- 
cludes. The fifth system is characterized by an oblique 
position of three unequal axes.* 



228 



229 



230 



^ ^ 




s 





774. The regular system, which is properly the first, 
has all its axes equal and all its angles right angles.f 
The figures which precede this paragraph represent 
some of its simpler forms. Those which follow, are 
among its most interesting combinations. In figure 233 
the student will be able to select three distinct kinds 



773. Define the third and fourth systems. 774. What are the charac- 
teristics of the regular system ? 



The variations of length and inclination of axes which correspond to the differ- 
ent systems, may be beautifully illustrated to the eye by a wooden frame work 
movable at the center with threads connecting the arms. 

t The first and sixth systems are made to change plaoes in the above arrangement, 
for the convenience of illustration from the quartz crystal. 



376 PRINCIPLES OF CHEMISTRY. 

of surfaces. One of these sets, if enlarged to the ex- 
clusion of the others, would produce a cube, another a 
regular octahedron, and a third a dodecahedron ; forms 
corresponding to those of figures 228, 229 and 230. 

231 232 233 ' 






In view of its simplicity, the regular system may be 
regarded as a sort of primitive architecture, yielding, 
however, to no other system in the beauty of its forms. 
Under one or the other of these systems all forms of 
crystals are included. To each of them, with the ex- 
ception of the regular system belong innumerable sets of 
forms according to the degree of inequality or inclination 
of the axes. Equality and rectangular position of the 
axes being characteristic of the first system, it is not 
susceptible of the sort of variation which is essential to 
produce different sets of figures. But in this, as in 
other systems, the modification of surfaces may occur 
to any extent. 

775. As the architect is able, from some relic of a 
broken column, to build up in imagination the temple 
of which it formed a part ; as the comparative anato- 
mist knows how, from the fragment of a single bone to 
reconstruct in imagination the perfect animal which 
possessed it ; so, from the merest point of a crystal, its 
complete form may often be readily inferred. In pro- 

775. Show how the form of a crystal may be inferred from its angles. 



CRYSTALS. 377 

portion as a double pyramid is lengthened out, the 
angles above and below are rendered more acute. 
From an accurate admeasurement of this angle its whole 
shape may therefore be inferred. Such admeasurement 
of various angles is employed not alone as a means of 
inference of perfect from imperfect shapes, but as the 
simplest means of accurate description. For, as before 
stated, the dimensions of the corresponding angles of a 
crystal form its characteristic. 

776. Isomorphism. — Many substances which are alike 
in the number and arrangement of their atoms, although 
these atoms are different in kind, have the same crys- 
talline form. This is the case with common alum and 
other alums to be hereafter mentioned. The similar 
arrangement of atoms will be best seen by inspecting 
the formula which represent them. 

Common Alum = KO,S0 3 ; Al 2 3j 3S0 3 ; 24HO. 
Ammonia Alum=JS T H 4 ; S03; Al 2 3} 3S0 3 ; 24HO. 
Soda Alum r=NaO,S0 3 ; Al a 8 ,3S0 8 ; 24HO. 

The potassium in common alum may be replaced, in 
whole or in part, by either soda, ammonia or lithia, and 
in the same manner the alumina may be replaced in 
whole or in part by the sesqui-oxide of iron, chromium 
or magnesium, and the crystalline form will be un- 
changed. All these compounds are therefore isomor- 
phous. 

The term isomorphism expresses their likeness in 
form. Besides this series there are many other isomor- 
phous groups. 

776. Have different substances ever the same crystalline form ? 



378 PRINCIPLES OF CHEMI8TKY. 

777. It is to be regarded as probable, that the shape 
and size of the molecules thus similarly composed is 
exactly the same, and that it is for this reason that they 
may be used in building up crystals of the same form. 
The different alums will even unite when they crys- 
tallize in building up one and the same crystal. Sub- 
stances which are thus similar in composition and 
crystallize in the same form, are called isomorphous. 
There are many cases of similar crystalline form in 
substances which are not thus related in other respects. 
Such bodies are not called isomorphous, notwithstand- 
ing their identity of crystalline form. Certain substan- 
ces crystallize in forms belonging to two or even three 
different systems, according to the temperature, or 
other circumstances under which their crystallization 
occurs. Such substances are called dimorphous or tri- 
morphous 

Oxides. 

778. The compounds of the metals with oxygen, with 
the exception of those which have decidedly acid prop- 
erties, are called oxides. "When a metal unites with 
oxygen in several different proportions, forming differ- 
ent oxides, these are distinguished as protoxide, deut- 
oxide or binoxide, tritoxide or teroxide : terms signify- 
ing first, second, and third oxides. The highest oxide 
is also called peroxide. An oxide containing three 
atoms of oxygen to two atoms of metal, is called a ses- 

777. Give the probable reason. 778. Define an oxide. By what terms 
are different oxides distinguished ? 



oxides. 379 

quioxide. The names of chlorides, sulphurets, &c, are 
similarly modified, to indicate the proportion of chlo- 
rine, sulphur, &c, which they respectively contain. 
Compounds of non-metallic substances with oxygen 
which do not possess acid properties, are also called 
oxides. There are, for example, oxides of nitrogen and 
phosphorus. 

779. Properties of Oxides. — The lower oxides are 
generally strong bases, while the higher oxides exhibit 
basic or acid properties according to circumstances. 
Binoxide of tin, for example, described in a previous 
chapter, acts as a base in combining with sulphuric acid 
to form a sulphate, while, if fused with potassa, it acts 
as an acid and forms a stannate. On account of its 
acid property, the binoxide of tin is also called stannic 
acid. The name is derived from Stannum, which is 
the Latin word for Tin. In general oxides require for 
their complete neutralization as many atoms of acid as 
they contain atoms of oxygen. Protoxides require one 
equivalent of acid to neutralize them. Sesquioxides, 
although weaker bases, require three equivalents of 
acid to form with them neutral salts, but such com- 
pounds are unstable and are easily decomposed. Basic 
oxides are in general devoid of all metallic appearance 
and present in the highest degree the qualities of earthy 
matters. Oxides, when found crystallized, are usually 
harder, less fusible, and less volatile than the metals 
which they contain. Potassa, protoxide of potassium, 
requires for its fusion a temperature but little less than 

779. What is said of acid and basic properties in oxides ? 



380 PRINCIPLES OF CHEMISTRY. 

that required for melting iron, although potassium as 
we have seen melts at a comparatively low temperature. 

780. Formation of Oxides. — Oxides may be formed 
directly by the union of oxygen and metal, or, indi- 
rectly, by separating them from some salts which con- 
tain them. Thus oxide of copper may be produced by 
simply heating copper in the air ; or, by precipitation 
from the nitrate, through the agency of potassa, or. 
thirdly, by simply heating the nitrate until all the acid is 
expelled. The oxides of tin and antimony are also 
directly produced, by the action of nitric acid on the 
metals. 

781. Hydrates, or Hydrated Oxides. — Oxides 
commonly combine in the act of precipitation with a 
certain proportion of water. The compounds thus 
formed are called hydrated oxides, or simply hydrates. 
The water may, in most cases, be separated from them 
by heat, and the uncombined oxide thus obtained. 

782. Conversion of Oxides. — When oxides are con- 
verted into chlorides, sulphurets, &c, by double de- 
compositions, to be hereafter described, the chlorides, 
sulphurets, &c, correspond to the oxides from which 
they are formed. Thus, protoxide of iron yields pro- 
tochloride, while sesquioxide yields sesquichloride. 

783. The Alkalies. — The oxides of potassium and 
sodium are called alkalies. They are known as potassa 
and soda, and are commonly obtained as hydrates. 



780. How are oxides formed ? Give examples. 781. What is a hydra- 
ted oxide ? 782. What is said of the conversion of oxides ? 783. Give 
some properties of the alkalies. 



OXIDES. 381 

They are white infusible substances from which the 
water connot be expelled by heat. They are soluble in 
water, and are the strongest of all bases. From their 
destructive action on animal matter, they are called 
caustio alkalies, and are often distinguished by this 
term from the carbonates of potassa and soda. Ammo- 
nia oxide of ammonium, is called a volatile alkali. 



Potassa. KO=47. 

784. Potassa is prepared from wood ashes. The ley 
obtained from these being evaporated to dryness, the 
mass which remains is the crude potash of commerce. 
This, when purified, becomes pearlash. 

785. Caustic Potassa. Hydrate of Potassa, KO,HO 
= 56. — Commercial potash and pearlash are both car- 
bonates of potash, from which the carbonic acid must 
be removed, in order to produce potassa itself. This is 
done by a milk of slaked lime. A solution of potash 
in at least ten parts of hot water, or a hot ley, made 
directly from wood ashes, should be employed in the 
experiment. To this the milk of lime is added, little 
by little, the solution boiled up after each addition, and 
then allowed to settle. If, after settling, a portion of 
the clear liquid is found no longer to effervesce on the 
addition of an acid, it is sufficient evidence that all the 
carbonic acid has been removed by the lime, and the 



784. What is the source of potassa ? 785. How is potassa prepared ? 
Give a modification of the above method. 



382 PRINCIPLES OF CHEMISTRY. 

process is completed* This must be ascertained by 
trial. About half as much lime as potash will be re- 
quired in the process. Caustic soda is similarly made 
from the carbonate of soda. 

The boiling in the above process may be omitted, 
if the mixture be frequently shaken up during several 
days. This modification of the method is much more 
234 convenient for the production of caustic 
alkalies in small quantities. Solutions, 
useful for a variety of chemical purposes, 
are thus obtained, and should be preserved 
for use. They may be converted into solids 
by evaporation, and the solid thus obtained 
fused and run into moulds. The commer- 
cial caustic potassa, occuring in slender sticks 
of white or grey color, is thus produced. It contains 
one equivalent of water and is properly a hydrate of 
potassa. 

235 786. Affinity of Potassa for "Water. — 

Ordinary potassa, as before stated, is a hy- 
drate. But its affinity for water is by no 
means yet satisfied in this form. If exposed 
in an open vessel, it rapidly attracts moisture 
from the air. It often dissolves, in the course 
of a few days, in the water thus obtained. 

787. Decomposition by Potassa. — Potassa added to 
the solution of almost any salt occasions a precipitate. 
The potassa takes the acid and precipitates the insolu- 

786. How can the affinity of patassa for water be proved? 787. What 
is said of the decomposition of salts by potassa? 





POTASSA. 383 

ble base. If the experiment is made with an ammonia 
salt, the base being volatile passes off into the air. 
Experiments may also be made with green 5 blue, and 
white vitriols, which are, respectively, sulphates of iron, 
copper and zinc. 

788. Cleansing PfwOperties of Potassa.- — If soiled 
rags are boiled with a dilute solution of potassa, they 
will be thoroughly cleansed by the process. The 
potassa unites with the acid of the grease contained 
in the cloth, and thus makes it soluble in water. 

789. Action of Potassa on Animal Matter. — 
Potassa is extremely destructive of animal matter. It 
readily dissolves the skin, as may be proved by rubbing 
a little between the fingers. If applied in sufficient 
quantity, it destroys the vitality of the flesh. It is 
often used for this purpose by surgeons. 

790. Effect on Vegetable Coloes. — Vegetable 
blues which have been previously reddened by acid, are 
restored to their original color by the action of potash 
and other alkalies. The blue pigment called litmus is 
the one most readily obtained. In preparation for the 
experiment, it is infused in hot water. The transfor- 
mation from blue to red and vice-versa may be repeated 
as often as desired, by the alternate addition of acid 
and alkali. Paper soaked in the red and blue liquids 
forms the test-paper of the chemist. It is used to indi- 
cate the presence of smaller quantities of acid and 

788. Illustrate the cleansing properties of potassa. 789. What is the 
action of potassa on animal matter? 790. How does potassa affect 
vegetable matter ? 



384 PRINCIPLES OF CHEMISTRY. 

alkali than could be recognized by the taste. An ex- 
tract of purple cabbage leaves, or the leaf itself, may 
be used in the above experiment. In this case the 
change of color by alkalies is from red to green. 

Soda. NaO=31. 

791. Properties of Soda. — The properties of soda 
are very similar to those of potassa, as above described. 
Caustic soda, like caustic potassa, is a hydrate repre- 
sented by the formula NaO,HO. Soda imparts a yel- 
low color to flame and gives a bright yellow line in the 
spectroscope ; potassa imparts to flame a beautiful violet 
color and gives a more diffused spectrum than soda, with 
a red line in the extreme red rays and a violet line in 
the extreme violet rays. 

Oxide of Ammonium. H 4 NO=18. 

792. Formation. — "When hydrated sulphuric acid 
combines with ammonia, the water which it contains is 
regarded as converting the ammonia into oxide of am- 
monium, with which the acid then combines. The 
action of other hydrated acids is the same. In naming 
the corresponding salts, the oxide of ammonium is 
called ammonia. Thus, the compound with sulphuric 
acid, is called sulphate of ammonia. It is to be borne 
in mind, that oxide of ammonium of such salts, con- 

791. What of the properties of soda ? 792. What is said of oxide of 
ammonium ? 



OXIDE OF CALCIUM. 



385 



tains a molecule of water in addition to the constitu-, 
ents of arnmoniacal gas. Nitrate of ammonia, for 
example, consists not simply of H 3 N,I^0 5 , but it con- 
tains in addition an equivalent of water which can- 
not be expelled by heat without the entire decomposi- 
tion of the salt. This nitrate is therefore looked upon 
as a nitrate of the oxide of ammonium and its formula 
is written H 4 NO,]Si0 5 . 

Oxide of Calcium, or Lime. CaO=28. 

793. Lime. — Lime or oxide of calcium is best obtained 
by heating chalk, marble 
or limestone. These are all 
carbonates of lime. Un- 
der the influence of a high 
temperature the tendency 
of the carbonic acid to 
assume the gaseous form 
is so increased, that the 
chemical affinities of the 
base are overcome. The 
carbonic acid escapes, leav- 
ing the caustic lime be- 
hind. This is the process 
of the ordinary limekiln. Figure 236 shows the most 
approved form of limekiln. The doors for the fuel, 
the fire grate and ash pit are shown at a,b,c,d. The 




793. How is lime obtained ? 



386 PRINCIPLES OF CHEMISTRY. 

, lime is removed at f while a new supply of limestone 
is added from time to time at the top of the kiln. 
The superior strength of potassa and soda as bases, is 
illustrated by the fact that the carbonic acid cannot be 
removed from them through the agency of heat. 

794. Hydrate of Lime; CaO,HO=37. — Slaked 
Lime. — When water is added to lime, one equivalent 
immediately combines with it and forms a hydrate. 
The hydrate, like that of potassa, is dry, although it 
contains a large portion of combined water. As the 
water thus becomes solid in the compound, its latent 
heat is given off to the air or surrounding objects. It 
has been recently proposed to employ the heat thus 
produced for culinary operations. If the process of 
slaking is conducted under a tumbler, with a slight sur- 
plus of water, steam will be produced. On lifting the 
tumbler, it will become visible by its condensation into 
vapor. Anhydrous sulphate of copper slakes like lime 
and changes from white to green. 

795. Ignition by Lime. — The heat thus produced is 
often sufficient to ignite gun-powder. It should be 
sprinkled on the mass and kept dry while the slaking 
proceeds. Warm water and well-burned lime should 
be employed in the experiment. Ships carrying lime 
are often set on fire by access of water to the lime, and 
buildings where it is stored are set on fire in the same 
manner. 



794. What is hydrate of lime ? 795. How may gunpowder be ignited 
through the agency of lime ? 



ALUMINA, MAGNESIA, &C. 387 

796. Action of the Air. — If lime is exposed to the . 
action of the air, it gradually combines with carbonic 
acid and water, and becomes converted into a mixture 
of hydrate and carbonate. It is then called air-slaked 
lime. By sufficiently long exposure the conversion 
into carbonate is complete. 

797. Lime in Mortar. — Ordinary mortar is a mix- 
ture of sand and lime. It hardens not simply by dry- 
ing, but by the absorption of carbonic acid from the 
air. A compound of hydrate and carbonate of lime, 
possessed of great hardness is thus produced. A gradual 
combination also takes place between the silica and the 
lime, which binds the two constituents still more firmly 
together. 

798. Hydraulic Cement. — If, in the preparation of 
lime, a limestone is used which contains a certain pro- 
portion of clay, (clay is a silicate of alumina), a double 
silicate of alumina and lime is produced. The com- 
pound has not alone the property of combining with 
water, like ordinary lime, but of becoming extremely 
hard and insoluble in the process. Such a lime is 
called hydraulic cement, and is used for building under 
water. Silica, magnesia, and some other substances 
impart the same property to lime. 

Alumina, Magnesia, &c. 

799. Alumina, &c. — Alumina, (Al 2 3 =51.5), so 
named from the corresponding metal, is insoluble, and 

796. What is the action of the air on lime ? 797. Why does mortar har- 
den? 798. What is hydraulic cement? 799. What is alumina ? 



388 PRINCIPLES OF CHEMISTRY. 

is called an earth. It is, like the peroxide of iron, a 
sesquioxide, containing three atoms of oxygen to two 
of metal. Natural alumina colored blue is called sap- 
phire. Colored red it forms the Oriental ruby. The 
topaz and the emerald are also compounds containing 
the same oxide. Baryta, strontia, lime and magnesia, 
are regarded as standing midway between the earth 
alumina and the alkalies and are called alkaline earths. 
They are more or less soluble, and possess the general 
properties of the alkalies in a diminished degree. Mag- 
nesia is sometimes classed as an earth. 

800. Other Metallic Oxides. — The remaining 
metallic oxides are powders of different colors. Most 
of them are insoluble. The more important have been 
already noticed in the Chapter on Metals. Their hy- 
drates may be obtained by precipitating solutions of 
their salts with potassa, soda, or ammonia. The hy- 
drate of the oxide of copper and peroxide of iron may 
serve as examples. The former is blue and the latter a 
reddish brown. 

801. The hydrated oxides of nickel, cobalt, tin and 
copper, produced from solution of these metals by the 
addition of ammonia, are again re-dissolved in an excess 
of ammonia. That of copper dissolves with a beauti- 
tiful blue color, which is conclusive evidence that the 
liquid with which the experiment is made contains cop- 
per in solution. 

802. Uses. — Oxide of magnesium or magnesia, and 

800. What are the properties of the other metallic oxides ? 801. Which 
hydrated oxides dissolve in ammonia ? 802. Give the uses of 6ome of 
the oxides. 



ALUMINA, MAGNESIA, &C. 389 

mercury, among others, are used in medicine, and white 
oxide of zinc, as a paint. Litharge or protoxide of 
lead is employed in making flint-glass and varnishes. 
Red lead is used as a paint. Oxide of bismuth is em- 
ployed as a cosmetic. 

803. Oxide of manganese is used to color glass pur- 
ple and violet. Oxide of cobalt, to color it blue ; oxides 
of copper, and chromium, to impart a green color to 
glass and porcelain ; peroxide of iron, to give it a yel- 
lowish red, and protoxide, a bottle-green. Sub-oxide 
of copper gives to glass a beautiful ruby red. Silver 
and antimony are employed to produce different shades 
of yellow and orange. Yiolet and rose color are ob- 
tained by means of the purple of Cassius, a beautiful 
purple precipitate, containing tin and gold, and pre- 
pared by adding protochloride of tin to a gold solu- 
tion. 

804. Glass Staining. — The effect of oxides, above 
mentioned, in coloring glass, may be illustrated by 
fusing them into a borax bead. The bead is to be formed 
with the aid of the blow-pipe, in a loop of platinum 
wire. In the absence of such wire, the borax glass 
may be made upon the surface of a pipe bowl. Instead 
of employing the oxide, it is generally more conveni- 
ent to moisten the bead with a very small 2g7 
quantity of a solution of the metal. In order 
to obtain good colors, the quantity of coloring 
material employed must be very small. 




803. What color is produced in glass by the oxide of manganese, co* 
bait, copper, iron, &c, &c. ? 804. How may these effects be illustrated? 



390 PRINCIPLES OF CHEMISTRY. 

805. For staining glass and porcelain superficially, a 
colored and easily fusible glass is first prepared with 
borax, or some analogous material. This being ground 
up and applied as a paint, is afterward baked into the 
surface. Several of the oxides mentioned in a preced- 
ing paragraph are thus employed. 

Chlorides. 

806. Description. — The chlorides are, for the most 
part, soluble salts, of colors corresponding to the solu- 
tions of the metals from which they are produced. 
Common salt, figure 238, may stand as a type 238 

of the class. Chloride of silver and subchloride 
of mercury or calomel are insoluble ; the chlo- 
ride of lead is but slightly soluble in water. 

807. Preparation. — Chlorides may be made by the 
action of chlorine or hydrochloric acid on the metals. 
The combustion of antimony in chlorine gas, the solu- 
tion of gold in aqua regia, and that of zinc in hydro- 
chloric acid are examples. The chemical action in each 
of these cases has been explained in previous chapters. 
The solutions being evaporated, the chlorides are ob- 
tained in the solid form. The solution of zinc in hy- 
drochloric acid is a case of single elective affinity : the 
metal elects or chooses the chlorine. 

808. Chlorides may also be formed by the action of 

805. How are glass and porcelain stained superficially ? 806. Describe 
some of the properties of chlorides. 807. How are chlorides made from 
metals ? Give examples. 808. How are chlorides produced from oxides ? 



CHLORIDES. 391 

hydrochloric acid on oxides. Thus common salt or 
chloride of sodium may be made by mixing hydrochlo- 
ric acid and soda. The hydrogen of the acid and the 
oxygen of the soda unite to form water, while the chlo- 
rine of the acid and the metal sodium unite to form the 
chloride. This is a case of double decomposition, re- 
sulting from double elective affinity. The chloride com- 
monly corresponds to the oxide from which it is pro- 
duced. Thus soda, which is a protoxide, yields common 
salt, which is a protochloride. Again, sesquioxide of 
iron, containing three atoms of oxygen to two of metal, 
yields sesquichloride of iron containing the same pro- 
portion of chlorine. 

809. The insoluble chlorides may be obtained directly 
in a solid form by a similar double decomposition. 
Thus, chloride of sodium and oxide of silver 
in solution yield, when mixed, a precipitate 
of chloride of silver • newly-formed oxide 
of sodium or soda remains in solution. The 
latter unites with the acid originally em- 
ployed to dissolve the oxide of silver. This 
is commonly nitric acid. 

810. Chloride of Sodium. KaCl=58.5. — Common 
Salt. — Common salt is found in great abundance in 
Poland and other countries, as rock salt, which is 
regularly mined like coal. An extensive deposit of salt 
almost entirely pure, perfectly white and much of it in 
transparent crystals, has been recently discovered in 

809. How are the insoluble chlorides obtained directly in a solid form ? 
810. From what sources is common salt obtained ? 




392 PRINCIPLES OF CHEMISTRY. 

Petite Anse Island near the mouth of the Mississippi 
River. Large transparent crystals of salt are found in 
the mines of Poland. Salt is also obtained by evapo- 
rating the water of the sea or salt springs, in the sun 
or by artificial heat. "When the salt water is boiled 
down the salt separates in crystals, while the impurities 
remain in the small portion of liquid which is not 
evaporated. These consist principally of chloride of 
magnesium and other salts. Boiling water dissolves 
but about one-seventh part more salt than water at the 
temperature of 32° Fahrenheit. 

811. "When salt is to be made from water which con- 
tains it in very small proportion, it is a frequent prac- 
tice in Europe, to pump the weak brine to the top of 
large heaps of brush, and allow it to trickle through 
them. The object of the method is to produce a large 
evaporating surface. The air, as it passes through the 
heaps, carries away a large part of the water and leaves 
the salt behind. The strong brine which is collected 
below is then boiled down, as before described. The 
annual produce of the salt springs at Syracuse, New 
York, is 9,000,000 bushels, and is constantly increasing. 

812. Beautiful crystals of common salt may be ob- 
tained by gradually evaporating a saturated solution. 
This will be accomplished by keeping it for some time 
moderately warm on a stove or in the sun. The pro- 
gressive development of crystals and their peculiar 



811. How is salt produced from very weak brine ? 812. How may crys- 
tals of salt be obtained ? 



CHLORIDES. 



393 



forms are represented in the figures. They are made 
of innumerable small cubes, which build themselves 





243 



regularly upon the edges as the 
larger crystals sink little by little 
into the solution. 

813. Uses of Common Salt. — The use of common 
salt in preserving the flesh of animals from decay, de- 
pends in part on the fact that it extracts from the flesh 
a large proportion of water. It thus, to a certain ex- 
tent, dries them. This action will be immediately 
observed if a little salt is sprinkled upon flesh. It will 
speedily draw out the juices of the meat and itself dis- 
appear by dissolving in them. By what action salt 
preserves meat is not fully known. 

814. Sea Water. — Every pound of sea water con- 
tains from one-half to five-eighths of an ounce of salt. 
The greater part of this is chloride of sodium or com- 
mon salt. The water of the Dead Sea contains a much 
larger proportion, and is more than an eighth part 
heavier than pure water. Owing to its greater density, 



813. How does salt act to preserve flesh ? 814. How much salt is con- 
tained in sea water ? in the water of the Dead Sea ? 



394 PRINCIPLES OF CHEMISTRY. 

a muscular man floats breast high in it without the 
least exertion. Fresh eggs, which sink in sea water, 
float in that of the Dead Sea with one-third of their 
length above the surface. 

815. Chloride of Lime. — .Bleaching Powder. — 
The commercial article of this name is prepared by- 
passing chlorine gas over lime. It is a white powder 
with an odor similar to that of chlorine gas. Its value 
depends on the fact that the gas is thus brought into a 
solid form and made capable of transportation. The 
best samples of commercial chloride of lime contain 30 
per cent, of chlorine. It may be released again by the 
simplest means, to be used as a bleaching and disaffect- 
ing agent. The addition of an acid, as has been seen 
in the chapter on Chlorine, is all that is necessary to 
effect this object. It occurs, indeed, spontaneously 
in the moistened powder, through the action of the 
carbonic acid of the air. 

816. Illustration. — To illustrate its bleaching power, 
a strip of calico may be soaked in a solution of the 
chloride, and then in acid water. Nascent chlorine is 
thus liberated in the fiber of the cloth, and is more 
effectual than if otherwise applied. 

817. Disinfecting Properties. — Chloride of lime is 
also used as a disinfectant. For this purpose it is placed 
in shallow dishes and moistened with water or dilute 
acid. The chlorine thus liberated at once destroys all 
noxious vapors. 

815. On what does the value of chloride of lime depend ? 816. How 
may its properties be illustrated ? 817. 



CHLORIDES. 395 

818. Form of Combination. — Chemists are not agreed 
in regard to the chemical action which occurs in the 
formation of chloride of lime. The mixture is, practi- 
cally, chlorine and lime, for as soon as an acid is added, 
all of the original lime unites with the acid and 
chlorine is evolved. 

819. Chloride of Aluminum. (AI 2 C1 3 =134.) — This 
salt is of peculiar interest and importance, in view of 
its employment in the preparation of the metal alumi- 
num. Alumina mixed with powdered charcoal is made 
into paste with starch or oil and divided into pellets, 
which are first charred in a covered crucible and then 
exposed to ignition in a current of dry chlorine. Car- 
bon in a finely divided state is thus intimately mixed 
with alumina. The alumina is torn asunder as it were 
by the affinities which are thus brought into play. The 
carbon takes its oxygen and passes off with it as car- 
bonic oxide, while the chlorine takes the metal and 
escapes with it as volatile chloride of aluminum which 
afterwards condenses in the cooler parts of the appara- 
tus as a crystalline, somewhat translucent mass, or as 
an amorphous powder. 

1820. Colored Flames. — A series of beautiful flame 
experiments may be made with the chlorides. The 
flame of alcohol assumes different colors according to 
the chloride employed. Chloride of sodium or common 
salt gives a yellow ; chloride of potassium, violet ; 
818. How are its elements combined ? 819. How is chloride of alumi- 
num prepared ? 820. What is said of colored flames ? 
■ 




396 PRINCIPLES OF CHEMISTRY. 

chloride of calcium, orange ; chloride of barium, yel- 
low; chloride of copper, blue. Instead of the chlo- 
rides, other soluble salts may be em- 
ployed with the addition of a little 
hydrochloric acid. A beautiful green 
may be obtained from a copper coin 
moistened with strong nitric acid, with 
the use of alcohol as before. The colors of fireworks 
are similarly produced by the addition of the above and 
certain other salts. 

821. Other Chlorides. — The other chlorides are not 
of sufficient general interest to be here particularly 
described. Corrosive sublimate, the uses of which are 
mentioned in the chapter on Mercury, is a chloride of 
this metal. Calomel is a subchloride of the same metal 
much used in medicine. 

Iodides, Bromides and Fluorides. 

822. The iodides and bromides are classes of salts 
analogous to the chlorides. Those of potassium used 
in medicine and in photography, are the most impor- 
tant. 

823. Detection of T .o o lo o o Iodine.— A beautiful blue 
is prepared by adding a little chlorine water and starch 
paste to a solution of iodide of potassium. The chlo- 
rine sets iodine at liberty, which then combines with 
starch to form the blue compound. By this test iodine 

821. What is said of other chlorides ? 822. What is said of the iodides 
and bromides ? 823. How is the blue iodide of starch prepared ? 




IODIDES, BROMIDES AND FLUORIDES. 397 

can be detected in a liquid which contains but a mil- 
lionth part of this element. By the substitution of 
bromide of pjotassium in the experiment, an orange 
color is produced. 

824. Test for Chlorine and Iodine. — The experi- 
ment may also be made by moistening a slip of paper 
with starch and iodide of potassium, and holding it in 
an atmosphere containing a little chlo- 
rine gas. An extremely small quan- 
tity of chlorine is thus indicated, and 
the prepared paper thus becomes a 
test for chlorine. Such paper is also 
used to show the presence of ozone in 
the air. 

825. Change of Color by Heat. — By mixing solu- 
tions of iodide of potassium and corrosive sublimate or 
chloride of mercury, a beautiful scarlet iodide of mer- 
cury is produced. On heating the dried precipitate 
it becomes yellow. The experiment is best made with 
two watch glasses. The iodide is heated in the lower 
one and collects by sublimation, with change color, in 
the upper. The same experiment may be performed 
by dipping a sheet of paper in the solution. On warm- 
ing the paper the iodide becomes yellow. 

826. Change of Color by Touch. — On touching 
the yellow incrustation with the point of a needle, it is 
immediately stained scarlet at the point of contact. 



824. How is this experiment employed as a test for chlorine ? 825. 
What is said of the iodide of mercury ? 826. What effect is produced 
by touching the yellow incrustation ? 



398 PRINCIPLES OF CHEMISTBY. 

The color gradually spreads, as if it were a contagious 
disease, through the whole mass, until every particle has 
regained its original scarlet. This experiment furnishes 
a very remarkable instance of change of an important 
property without change of composition. As the change 
of color proceeds, the small scales of which the yellow 
iodide is composed break up into octahedrons. The 
yellow iodide upon the paper prepared as in the pre- 
ceding paragraph, will also turn red on being rubbed. 
The change of color is regarded as a consequence of 
the re-arrangement of atoms, which produces the change 
of form. 

Fluorides. 

827. Flttor-spar. — The fluorides, with the exception 
of those of the alkalies, are for the most part white in- 
soluble compounds. The only one of especial interest, 
is the beautiful mineral known as fluor-spar. This 
mineral is a fluoride of calcium. It is found of white, 
green, purple and rose color, crystallized in 247 
regular cubes or octahedrons. Hydrofluoric 
acid, which has the remarkable property of 
etching glass, as before described, is prepared 
from it. 

Sulphurets. 

828. The compounds of the metals \tfith Sulphur are 
called sulphides or sulphurets. They are of various 

827. What is said of fluor-spar ? 828. Define a sulphuret ? 



SULPHUEETS. 390 

colors, and, for the most part, insoluble. Iron pyrites 
and galena or sulphuret of lead, are examples. The 
figure represents a crystal of magnetic 
pyrites, which is one of the sulphurets 



of iron. The form belongs to the sixth Q ^f Q 

or hexagonal system. 

829. Preparation. — Most of the sulphurets may be 
produced by adding hydrosulphuric acid to solutions 
of the different metals or their salts. Sulphur and 
metal unite and precipitate, while the hydrogen and 
oxygen, previously combined with them, form water. 

830 The sulphuret of zinc is white ; that of arsenic, 
yellow ; and that of antimony, orange. The remainder 
of the insoluble sulphurets are black. Solu- 
tions of white vitriol, arsenious acid, and 
tartar emetic may be used, as above directed, 
to produce sulphurets of zinc, arsenic and 
antimony. If the zinc precipitate should be 
colored, it is owing to the presence of iron in 
the salt, as impurity. Blue vitriol may be employed to 
produce black sulphuret of copper. 

831. The sulphurets of ammonium, potassium and 
sodium cannot be precipitated by this process. Being 
soluble, they remain in the liquid. Solutions of the 
caustic alkalies are to be used in preparing them. The 
solutions of these sulphurets are useful, as they may, in 
many cases, be substituted with advantage for hydro- 



829. How are sulphurets generally prepared ? 830. Mention the colors 
of some of the sulphurets. 831. What is said of the sulphurets of the 
alkalies ? 




400 PRINCIPLES OF CHEMISTRY. 

sulphuric acid in precipitating sulphurets from solutions 
of other metals. Certain other sulphurets are soluble 
and do not precipitate, as will be seen from the table in 
the Appendix. 

832. Liyer of Sulphur. — There are a number of 
sulphurets of potassium, containing each a different 
proportion of sulphur. That which contains five atoms 
of sulphur to one of metal is called, from its peculiar 
color, liver of sulphur. It is prepared by boiling 
flowers of sulphur in a strong solution of potash. It 
may also be made by fusion of the same materials. 
The protosulphuret can be made from the sulphate, by 
reduction with hot carbon. Certain other soluble sul- 
phurets may be produced in the same manner. 

833. Milk of Sulphur. — This form of sulphur, like 
that just mentioned, is used in medicine. It may be 
prepared from a solution of the liver of sulphur, by the 
addition of an acid. The latter combining with the 
potassa, the sulphur is precipitated in a state of the 
finest division, giving to the liquid the appearance of 
milk. 

834. Other Sulphurets. — The natural sulphurets 
have colors different from the similar compounds when 
produced, as above, by precipitation. Thus, the natural 
sulphuret of lead or galena has the color of the metal ; 
that of mercury is red, and is called cinnabar ; that of 
zinc, called zinc blende, and by miners black jack, is of 
different shades — brown, yellow and black. The pre- 

832. What is liver of sulphur ? How is it prepared ? 833. How is 
milk of sulphur prepared ? 834. What is said of the other sulphurets ? 



SULPHATES. 401 

cipitated sulphuret of mercury turns red by sublima- 
tion, and in this state forms the familiar pigment called 
vermilion. Sulphuret of iron, which is employed in 
making hydrosulphuric acid, may be prepared by hold- 
ing a roll of sulphur against a rod of iron previously 
heated to whiteness. This may be readily done in any 
blacksmith's shop. The fused sulphuret falls in glo- 
bules from the surface of the iron. 

Sulphates. 

835. The sulphates, with the exception of those of 
the alkaline earths, are, for the most part, soluble salts. 
They are similar in color to the solutions of the corres- 
ponding metals. The sulphates of the alkalies and of 
the alkaline earths are not decomposed when heated to 
redness, except sulphate of magnesia which loses part of 
its acid. The sulphates of zinc, cadmium, nickel, co- 
balt, copper and silver require an intense heat to decom- 
pose them. Other sulphates part with their acid when 
strongly heated. Sulphuric acid, called oil of vitriol, 
may be obtained by heating sulphate of iron, called 
green vitriol, § 413. 

836. Preparation. — The soluble sulphates are pro- 
duced either by the direct combination of sulphuric 
acid with the proper oxide, or by its action on the 
metals.* The latter has been already particularly de- 
scribed in the section on Sulphuric acid. The insolu- 

835. What is said of the color and solubility of sulphates ? 836. How 
are the sulphates formed ? 



402 PRINCIPLES OF CHEMISTRY. 

ble sulphates, such, as those of baryta and lead, may be 
obtained by precipitating a soluble salt of the base by 
means of some soluble sulphate, such as sulphate of 
soda. They are also sometimes formed in nature by 
the action of the air on sulphurets. In this action the 
metal is converted into oxide, and the sulphur into acid, 
which together form the sulphate. Green vitriol is 
sometimes thus formed in soils from sulphuret of iron 
orfooVs gold. 

837. Sulphate of Lime. (CaO,S0 3 =68): Gypsum 
(CaO,S0 3 ; 2HO = 86.)— This is a white, soft mineral 

249 occurring abundantly in nature. The figure 
represents a crystal of gypsum. The form be- 
longs to the fourth system. The finer kinds 
are known as alabaster. "When it occurs in 
flat transparent prisms it is called selenite. Sul- 
phate of lime free from water of crystallization 
occurs in the mineral called anhydrate, crystallized in 
regular rectangular prisms, which are found in the salt 
rocks of the Tyrol, and in Upper Austria. Finely 
ground sulphate of lime is employed extensively as a 
fertilizer of the soil under the name of plaster. Plas- 
ter of Paris is produced by heating gypsum until its 
water is expelled. The plaster, when pulverized, has 
the property of setting with water, or, in other words, 
forming a hard coherent mass. 

838. Plaster Casts. — Plaster casts are made by re- 
ducing burned or powdered gypsum to the consistence 

837. What is gypsum ? 838. How are plaster casts produced ? 



SULPHATES. 403 

of cream, with, water, and then pouring it into moulds. 
A coin may be copied by pouring such a paste into a 
small paper box containing the coin. Two parts of 
ordinary ground gypsum, heated moderately until vapor 
ceases to escape, and then mixed with one part of 
water, form a good proportion. The heat should not 
be carried very far beyond that of boiling water, or the 
plaster refuses to set. 

The hardening of the plaster takes place very rap- 
idly. It is owing to the re-combination of the material 
with, water. The water thus absorbed exists in a solid 
form in the compound, as in other salts. 

839. Aluminated Plaster. — Harder and better casts, 
more nearly resembling marble, are made by steeping 
the burned gypsum for six hours in strong alum water, 
and then re-heating it at a higher temperature. After 
being again pulverized, it may be used like ordinary 
plaster, but requires more time to harden. 

840. Sulphate of Soda. (K~aO,S0 3 ). — Glauber's 
Salt. — This is a white salt forming 

crystals belonging to the third system 



such as are represented in the figure. Q ^ 

It is used to some extent in medicine, 
and in large quantities for the production of carbonate 
of soda. It is prepared by pouring oil of vitriol upon 
common salt. A double decomposition takes place be- 
tween the salt and the water of the acid ; hydrochloric 
acid is formed, which passes off, and soda, which re- 
Why do plaster casts harden? 839. What is aluminated plaster? 
840. Describe sulphate of soda, and its preparation. 



404 PRINCIPLES OF CHEMISTRY. 

mains combined with the sulphuric acid. It is to be 
understood that this reaction between water and com- 
mon salt, takes place only when sulphuric acid is pres- 
ent. The method of making the experiment is given 
in the paragraph on the preparation of hydrochloric 
acid: 

841. Sulphate of soda may be obtained in crystals 
by evaporation. Three forms of sulphate of soda may 
be obtained in crystals. The ordinary form contains 
10 equivalents of water. Another form contains 7 
equivalents of water and still another form contains no 
water. These crystals, like those of many other salts, 
lose their combined water on exposure to the air and 
become converted into a white powder. This change 
is called efflorescence, and the salt which experiences it 
is called efflorescent. In preparing the salt on a large 
scale, for conversion into carbonate of soda, great quan- 
tities of hydrochloric or muriatic acid are incidentally 
produced. 

842. Sulphate of Baryta. (BaO,S0 3 ) — The sul- 
phate of baryta is a white insoluble substance, which 
may be obtained as a precipitate, by double decomposi- 
tion of any soluble baryta salt with a soluble sulphate. 
It is a mineral of frequent occurrence, known as heavy 
spar. It is used for the adulteration of white lead, in 
which it may be easily detected as a residue, on dissolv- 
ing the white lead in dilute nitric acid. The sulphate 
of lead is another of the few insoluble sulphates. 

841. What is said of its crystals ? 842. What is sulphate of baryta ? 
How prepared ? Uses ? 




SULPHATES. 405 

843. Alum. — Ordinary alum is'a double sulphate of 
alumina and potassa. (KO,S0 3 ; A1 2 3 3S0 3 ; 24HO). 
Solutions of the two salts, when mixed, combine to form 
the double salt. The sulphate of alumina required in 
the process may be obtained by dissolving alumina from 
common clay by sulphuric acid. Or it may be pro- 
duced by exposing certain clays or slates 251 
which contain sulphuret of iron to the 
action of the air. Under these circum- 
stances the sulphur becomes converted 
into sulphuric acid, which unites with 
both oxide of iron and alumina. From this mixture 
the protosulphate of iron is separated by crystallization, 
leaving a solution of sulphate of alumina to be used in 
the preparation of alum. 

844. On heating alum in a, crucible or pipe-bowl, it 
swells up into a light porous mass and is con- 252 
verted into hurnt alum. At the same time it 
loses its water of crystallization, of which it 
contains twenty-four molecules to each mole- 
cule of the double sulphate. Common alum has a sweet- 
ish astringent taste; it is soluble in 18 parts of cold 
water and in less than its own weight of boiling water. 
It retains 4 equivalents of water even at a temperature 
of 248°. At 392° it loses all its water and at a red 
heat the salt is decomposed. Alum is much used as a 
mordant in dyeing and for tanning the lighter kinds of 
leather. 

843. Describe alum, and its preparation. 844. What is burnt alum ? 




406 PRINCIPLES OF CHEMISTRY. 

845. Other Alums. — The name alum is applied to a 
number of salts having a composition analogous to the 
common alum already described. In one of these, ses- 
quioxide of chromium, and in another, sesquioxide .of 
iron, takes the place of the alumina or sesquioxide of 
aluminum. In a third kind of alum oxide of ammonium 
replaces the potassa. All of these alums contain the 
same number of molecules of water of crystallization. 
They have all the same crystalline form, and, if mixed 
in solution will crystallize together. They are, there- 
fore, isomorphous salts. Their perfect analogy of com- 
position will be best seen by the inspection of their 
formulae, as follows : 

Potash alum, KO,S0 8 ; A1 2 3 , 3S0 3 ; 24HO. 
Ammonia alum, H 4 NO,S0 3 ; A1 2 3 ,3S0 3 ; 24HO. 
Soda alum, NaO,S0 3 ; A1 2 3 ,3S0 3 ; 24HO. 

Iron alum, KO,S0 3 ; Fe 2 3 ,3S0 3 ; 24HO. 

Chrome alum, KO,S0 3 ; Cr 2 3 ,3S0 3 ; 24HO. 
Manganese alum, KO,S0 3 ; Mn 2 3 ,3S0 3 ; 24HO. 

846. Persulphate of Iron. — Moistsel's Salt. — 
(Fe 2 3 ,3S0 3 ). To one equivalent of protosulphate of iron 
in solution, one half an equivalent of oil of vitriol is 
added, the solution is boiled and nitric acid is added in 
small quantities as long as any red fumes are given off. 
By evaporation on glass plates, at a moderate tempera- 
ture, the persulphate of iron is obtained in yellowish 
brown deliquescent scales, which are used in surgery as 
the most valuable agent known for arresting hemor- 
rhage. 

845. What is said of other alums ? 846. What is said of persulphate of 
iron? 




NITRATES. 407 

847. Other Sulphates. — Vitriols. — Several of the 
sulphates have received the common name of vitriols. 
Sulphates of zinc, copper, and iron are called 258. 
respectively white, blue, and green vitriol. 
Green vitriol readily absorbs oxygen from the 
air, and becomes brown, from the accumula- 
tion of peroxide of iron upon its surface. A 
solution of it is changed to a yellowish-red 
color by the oxidizing action of either nitric acid or 
chlorine. A crystal of blue vitriol is represented in 
the figure. The form belongs to the fifth system. 

"White anhydrous sulphate of copper slakes like lime 
with evolution of heat when water is applied, and at 
once changes to a beautiful green color. The sul- 
phates of zinc and of copper are both powerful emetics 
and they are also both useful applications to inflamed 
and ulcerated surfaces. 

Nitrates. 

848. The nitrates are formed by the action of nitric 
acid on metals, as already explained, and also 254 
by the action of the acid on oxides previously /r\ 



formed. In the latter case, the metallic oxide 
takes the place of the water of hydration 
which always belongs to the acid. They are 
also produced by double decomposition. This \/y 
latter method is illustrated below, in the preparation of 
nitrate of potassa from the nitrate of lime. The fig- 
ure represents a crystal of saltpetre. The form be- 
longs to the third system. 

847. What is said of vitriols ? 848. How are nitrates formed ? 



408 PRINCIPLES OF CHEMISTRY. 

849. Nitrate of Lime. (CaO,N0 5 ; 4110 = 82 + 36= 
118). — This salt is of considerable interest, from the 
fact that it is employed in the production of saltpetre 
or nitre. It is formed in the so called, nitre heds, by 
mixing together refuse animal matter with earth and 
lime. In the gradual putrefaction of the animal mat- 
ter which follows, its nitrogen takes oxygen from the 
air, and is converted into nitric acid. The acid then 
combines with the lime to form the nitrate. The salt 
is afterward extracted by water. The formation of 
nitric acid, above mentioned, takes place only in the 
presence of alkaline substances. In their absence the 
nitrogen passes off, combined with hydrogen, as ammo- 
nia. Even in the presence of lime, there is reason to 
believe that ammonia is first formed, and its constitu- 
ents afterwards converted into nitric acid and water. 

850. Nitrate of Potassa. — Nitre or Saltpetre. 
(KO,jN"O 5 =101.) — This salt is a constituent of certain 
soils, especially in warm climates. These soils always 
contain lime, and are said to be never entirely destitute 
of vegetable or animal. matter. It is obvious, therefore, 
that nitrate of potassa may be formed in them, as the 
same salt of lime is formed in the nitre beds just de- 
scribed. A small proportion of nitric acid exists in the 
atmosphere, combined with ammonia. This, also, may 
be a source of part of the nitric acid of the nitrous 
soils. Again, it is probable that nitric acid is slowly 
formed from the atmosphere by the direct combination 

849. How is nitrate of lime produced ? 850. Explain the formation 
of nitre. 



NITRATES. 409 

of its elements in the porous soil. Nitre, on being 
highly heated, yields a third of its oxygen in the form 
of gas. 

851. Nitre is obtained from nitrous soils by lixivation 
with water and subsequent crystallization. From ni- 
trate of lime, it is produced by double decomposition 
with carbonate of potassa. Carbonate of lime precipi- 
tates, while nitrate of lime remains in solution. This 
may be afterward poured off, evaporated, and crystal- 
lized. 

852. Uses of Nitke. — Nitre is extensively employed 
by the chemist and in the arts, as an oxidizing agent. 
A few grains of it introduced into a solution of green 
vitriol or sulphate of iron, to which some free sulphuric 
acid has been added, will immediately change its color. 
The sulphuric acid sets nitric acid at liberty, to which 
the oxidation and change of color are to be attributed. 
Mtre, when heated, yields part of its oxygen, as before 
stated. If heated with metals, it converts them into 
oxides. The principal use of nitre is in the manufac- 
ture of gun-powder. 

853. Gun-powder. — Gun-powder is a mixture of 
nitre, charcoal, and sulphur. When ignited, the carbon 
burns instantaneously, by help of the oxygen of the 
nitre, thus producing a large volume of carbonic acid 
gas. To this gas, together with the nitrogen which is 
also set at liberty at the same moment, the force of the 

851. How is nitre obtained from nitrous soils ? 853. Mention some of 
the uses of nitre. 853. Explain the action of the different constituents 
of gunpowder. 



410 PRINCIPLES OF CHEMISTRY. 

explosion is due. The sulphur at the same time com- 
bines with the potassium of the nitre, and remains with 
it as a sulphuret of potassium. Gunpowder =C 3 S + 
KO^NOs become after ignition =3CO+B" + SK Three 
equivalents of carbon to one of nitre and one of sulphur 
expresses very nearly the composition of gunpowder. 
It varies, however, according to the uses for which it is 
intended, and the country in which it is manufactured. 
From the proportion, by equivalents, the relative weight 
of the constituents can readily be calculated. 

854. Collection of the Gases. — For the produc- 
tion and collection of the gases evolved in the com- 

255 bustion of gunpowder, the fuses 

of ordinary "fire-crackers" may 
be employed. Several of them 
are to be ignited at the same 
time in an ordinary test-tube. 
The mouth of the latter being 
then brought under a filled and 

inverted vial, the gases are collected as fast as they are 

evolved. 

855. Nitrate of Ammonia. (H 4 NO,NO 5 =80.)— 
Nitrate of ammonia may be prepared from the carbo- 
nate by the addition of nitric acid, and subsequent 
evaporation. The nitric acid decomposes the carbonate 
of ammonia and the carbonic acid escapes as a gas 
while the nitric acid unites with the ammonia. This 



854. How are the gases collected ? 855. How is nitrate of ammonia 
prepared and fbr what is it used ? 




CARBONATES. 411 

salt is used for the preparation of laughing gas. See 
section 445. 

856. Titrate of Silver. (AgO,NO 5 =170.) — Ni- 
trate of silver or lunar caustic is employed in surgery, 
for cauterizing wounds. Nitrate of silver is also ex- 
tensively used in photography. A solution of the salt 
in which the oxide has been precipitated by ammonia 
and re-dissolved by a slight excess, is extensively em- 
ployed as an indelible ink. The black color comes from 
oxide of silver and finely divided metal precipitated in 
the cloth. It may be removed by soaking in a solution 
of common salt, and thus converting the silver of the 
mark into chloride of silver. This is soluble in ammo- 
nia, and may be afterward extracted by that agent. 
Nitrate of silver is also the basis of most dyes for the 
hair. 

857. Other Nitrates. — Nitrate of soda (NaO,N0 5 
= 85) is a white salt, found native in South America. 
It is used in the manufacture of nitric acid, and, to 
some extent, as a fertilizer of the soil. The remaining 
nitrates are soluble salts, of colors corresponding to the 
solutions of the metals, as already described. The 
uses of the nitrates of silver and bismuth have already 
been mentioned. 

Carbonates. 

858. Carbonates. — The carbonates are, for the most 
part, white or light colored salts, of which chalk may 

856. Describe nitrate of silver. What are its uses ? 857. Describe the 
other nitrates. 858. Describe the carbonates. 



412 PRINCIPLES OF CHEMISTRY. 

serve as an example. The carbonate of copper is found 
native, both as blue and green malachite. All of the 
carbonates, excepting those of the alkalies, may be de- 
composed by heat. The latter are soluble and retain 
their acid at the highest temperatures. 
• 859 Preparation. — The insoluble carbonates may 
be produced by precipitating solutions of the metals or 
their salts by carbonic acid or solutions of the alkaline 
carbonates. In the latter case a double decomposition 
occurs with exchange of acids and bases. 

880. Carbonate of Potassa. (KO,C0 2 :=69).— 
Potash. — The method of preparing potash and pearl- 
ash, from wood ashes, has already been considered in 
the paragraph on Potassa. Saleratus is a carbonate 
containing a large proportion of carbonic acid. Its use 
for " raising" bread and cake is familiar. The acid em- 
ployed with it, sets the carbonic acid gas at liberty and 
thus puffs up the " sponge." 

861. Carbonate of Soda. (]STaO,C0 2 =53.)— Soda. 
— Carbonate of soda is commonly known under the 
name of soda. It is a white soluble salt, familiar from 
its use in Seidlitz and soda powders. Its carbonic acid 
is the source of the effervescence in these preparations. 
The bicarbonate or supercarbonate of soda, JSTaO,IIO, 
2C0 2 is the form of soda in common use. 

862. Carbonate of soda is prepared from the sulphate 
of soda. This salt being heated with charcoal is con- 



859. How are the insoluble carbonates prepared ? 860. What is said 
of carbonate of potassa ? 861. Describe carbonate of soda. 862. How 
is carbonate of soda prepared ? 



CARBONATES. 



413 




verted into sulphide of sodium. On heating the latter 

with carbonate of lime, a double decomposition occurs, 

and carbonate of soda is produced, with sulphide of 

calcium as an incidental product. Both parts of the 

process are combined in 

practice. Sulphate of soda, 

chalk and coal, are heated 

together in a reverberatory 

furnace, the carbonate of 

soda is then dissolved out 

from the fused mass, dried, 

purified, and subsequently 

crystallized. The sulphide of calcium would dissolve 

at the same time, and thus defeat the process, were it 

not rendered insoluble by combination with a certain 

quantity of lime. 

863. Another method of manufacturing carbonate of 
soda, consists, essentially, in separating sulphur from 
the sulphate, by means of oxide of iron, and substitu- 
ting carbon in its place. In this process also, the mate- 
rials are heated with charcoal, in a reverberatory fur- 
nace, and the carbonate afterward extracted by water. 
The impure uncrystallized carbonate of soda, is known 
in commerce as soda ash, and is largely employed in 
the manufacture of hard soap and in other processes. 

864. Carbonate of Ammonia. — Sal Volatile. — 
The ordinary sal volatile of the shops, used as smelling 
salts, is a carbonate containing three equivalents of acid 
to two of base. (2NH 4 0,3C0 2 + 2Aq). This is really 



863. Describe another method. 864. What is sal volatile ? 



414 PRINCIPLES OF CHEMISTRY. 

a sesquicarbonate. It wastes away gradually in tlie 
air, and passes off in a gaseous form. 

865. Preparation. — Sal volatile is prepared by heat- 
ing together carbonate of lime and chloride of ammo- 
nium. Carbonate of ammonia immediately passes off, 
while chloride of calcium remains behind. The car- 
bonate is led into a cold pipe or chamber, where it takes 
the solid form. The mixture of chalk and sal ammo- 
niac is sometimes used as smelling salts. The produc- 
tion of sal volatile from the mixture is very gradual if 
heat is not applied. 

257 866. The property from which the salt re- 

ceives its name, may be illustrated, by hold- 
ing in its vicinity a rod or roll of paper 
moistened with strong muriatic acid. A 
dense cloud of sal ammoniac is immediately 
produced in the air, from the union of the 
two vapors. The experiment is more strik- 
ing, if the sal volatile is warmed in a cup or other ves- 
sel. This salt is sometimes used by bakers for making 
bread and cakes light and spongy. 

867. Carbonate of Lime. (CaO,CO 2 =50). — Carbo- 
nate of lime, in the form of chalk, marble and ordinary 
limestone, is a most abundant mineral. Whole moun- 
tain chains consist of the latter rock. The shells of 
shell-fish are principally carbonate of lime. There is 
good reason, indeed, to believe that all- limestones have 
their origin in accumulations of such shells, which have 

865. How is sal volatile prepared? 866. How is it proved to be vola- 
tile ? 867. What is said of carbonate of lime ? 






CARBONATES. 415 

been consolidated in the course of ages. The figure 
represents a crystal of carbonate of lime or calc spar. 
The finest crystals of this mineral are ob- 
tained from Iceland, and are hence called 
Iceland spar. 

868. Solubility in Carbonic Acid. — 
The solubility of carbonate of lime in carbonic acid is 
readily shown, by passing a current of the gas through 
water clouded with pulverized chalk ^£59 
or marble. Other mineral substances 
which form the food of plants are dis- 
solved by the same means, and then 
find their way into the roots, to sub- 
serve the purposes of vegetable life. 

869. Incrustations in Boilers. — Carbonate of lime 
dissolved in carbonated water is again precipitated on 
boiling the solution. This is owing to the escape of 
the acid. Incrustations in tea-kettles and steam-boilers, 
in limestone districts, owe their origin to the same cause. 
In some cases the crust is formed of gypsum or other 
earthy matters contained in the water. One method 
of avoiding this inconvenience in steam-boilers, is by 
the addition of a smaller boiler in which the water is 
first heated and its sediment deposited. 

870. Stalactites. — The masses of carbonate of lime 
which hang like mineral icicles from the roofs of cav- 
erns, Figure 260, are called stalactites. The water that 



868. How is the solubility of carbonate of lime in carbonic acid 
shown ? 869. What is said of incrustations in boilers ? 870. What are 
stalactites ? 



416 



PRINCIPLES OF CHEMISTRY. 



260 



penetrates the soil is the architect of these curious 
forms. Impregnated with carbonic acid derived from 

decaying vege- 
tation, it takes 
up its load of 
carbonate of 
lime as it set- 
tles through the 
rock, and de- 
posits it again 
on exposure to 
the air of the 
cavern, in various and often fantastic shapes. Another 
portion of water, dripping to the floor of the cavern, 
builds up similar forms, called stalagmites, from below. 
871. Artificial Marble. — The surface of wood or 
stone may be marbled by covering it with successive 
coats of milk of lime, and allowing each in turn to dry 
before the next is applied. The surface is then smoothed 
and polished, and carbonic acid finally applied by which 
it is converted into marble. The milk of lime is simply 
a mixture of slaked lime and water, and may be so 
colored as to produce a variegated surface. 




Phosphates. 

872. Phosphates. — The phosphates, with the excep- 
tion of those of the alkalies, are, for the most part, 
white insoluble salts. Ordinary phosphoric acid has 



871. How is artificial marble produced ? 872. Describe the phosphates. 



PHOSPHATES. 417 

the property of combining with and neutralizing three 
equivalents of base, instead of one, as is the case with 
most other acids. It is therefore called a tr (basic acid. 
The hydrated acid contains, also, three equivalents of 
water, and may be regarded as a salt in which the water 
acts the part of base. Arsenic acid is similar in this 
respect, as well as in the amount of oxygen which it 
contains and in the salts which it forms with bases. 
Two other kinds of phosphoric acid may be prepared 
from that above mentioned; the first combines with 
one, and the second with two equivalents of base. The 
phosphates which contain two equivalents of base to 
one of acid are called pyrophosphates, because the acid 
has been modified by the action of fire upon the triba- 
sic phosphate of soda. 

873. Preparation. — The phosphates of the alkalies 
may be produced by the action of phosphoric acid on 
the proper carbonates. The remaining phosphates may 
be precipitated by solution of phosphate of soda from 
solutions of the metals or their salts. As in other cases 
of precipitation, there is here a double decomposition 
with exchange of acids and bases. 

874. Phosphate of Lime. — A tribasic phos- 261 
phate of lime (2CaO,HO,P0 5 + 3Aq) occurs 
naturally crystallized in hexagonal prisms, 
which when colorless are called apatite and 
when green moroxite. These crystals contain, 
besides phosphate of lime, a variable quantity of fluoride 

873. How are the phosphates prepared ? 874. In what mineral does 
phosphate of lime occur ? What is bone-ash ? 



418 PRINCIPLES OF CHEMISTRY. 

of calcium. The most important variety of phosphate 
of lime is that called bone ash, which is obtained by 
calcining bones, the phosphate of lime being the prin- 
cipal earthy ingredient of the animal skeleton. 

875. Superphosphate of Lime. — A mixture bearing 
this name, formed by the action of dilute sulphuric acid 
on burned bones, is extensively used as a fertilizer of 
the soil. The sulphuric acid, when added, appropriates 
part of the lime of the bones, forming with it gypsum ; 
at the same time, it leaves the phosphoric acid which it 
displaces free to combine with another portion of phos- 
phate of lime and thereby to render it soluble. The 
commercial article is a mixture of this soluble substance 
with the gypsum and animal charcoal produced in its 
formation. Other materials are often added, increasing 
or diminishing, according to their nature, its agricultu- 
ral value. The basis of the manufacture is commonly 
the refuse bone black of sugar refineries. 

876. Other Phosphates. — The phosphate of soda is 
used in medicine, and by the chemist to produce 
other phosphates. The phosphate of silver 
is a beautiful yellow precipitate, obtained by 
precipitating salts of silver with phosphate of 
soda or any other salt containing phosphoric 
acid. Pyrophosphate of iron is also much 

used in medicine. 



875. Describe the preparation of superphosphate of lime. 876. What 
is said of other phosphates ? 




SILICATES. 419 



Silicates. 



877. The silicates form an exceedingly large class of 
salts and are most abundant natural productions. All 
the forms of clay, feldspar, mica, hornblende, steatite 
or soapstone, and a large number of other common 
minerals, are silicates. Meerschaum, from which pipe- 
bowls are often manufactured, is a hydrous silicate of 
magnesia. Silicates are for the most part insoluble, 
and are variously colored. Mica and feldspar, two of 
the constituents of granite, may serve as examples. As 
components of this and other rocks the silicates make 
up a very large portion of the mass of the earth. 

878. Preparation. — Most silicates may be artificially 
formed by fusing together quartz sand and the proper 
oxide. This is done in the manufacture of glass, to be 
hereafter described. Slags, which occur as a by-product 
in the reduction of metals from their ores, are artificial 
silicates. Silicates may also be formed by precipitating 
solutions of metals or their salts by the solution of an 
alkaline silicate. Most of the silicates are fusible at a 
high temperature, their fusibility increasing by mixture 
with each other. Those which contain readily fusible 
oxides melt at the lowest temperature, and in general 
the basic silicates fuse more readily than those which 
are neutral or contain an excess of acid. 

879. Clay. — All the varieties of clay are silicates or 
hydrated silicates of alumina ; they are frequently 

877. What is said of silicates ? 878. How are silicates prepared ? 879. 
What is the composition of clay ? 



420 PRINCIPLES OF CHEMISTRY. 

largely mixed with other substances. Clay results 
chiefly from the breaking down and disintegration of 
feldspathic rocks. Clay emits the peculiar odor known 
as argillaceous when breathed upon or slightly moist- 
tened. Its plastic qualities render it highly valuable. 

880. Varieties of Clay. — Kaolin, the celebrated 
porcelain clay of China, is perfectly white and is nearly 
pure silicate of alumina. It is now found in several 
localities. The coarser varieties of clay usually contain 
oxide of iron, which gives them a yellow color when 
hydrated and red when anhydrous. 

Pipe-clay is a white variety nearly free from iron. 
Some clays are colored blue by the presence of organic 
matter which is destroyed when heated. 

Yellow Ochre and Bed Bole are clays which derive 
their color from oxide of iron, which is present in large 
quantity. 

Fuller's Earth is a porous silicate of alumina which 
has a strong adhesion to oily matters. When the pro- 
portion of carbonate of lime in a clay is considerable 
it constitutes what is known as a marl. 

881. Soluble Glass. — Soluble glass is made by fus- 
ing sand with potassa or soda. Its production may be 
illustrated in a soda bead, by subsequently re-fusing it 
with addition of sand. As the silicic acid combines 
with the soda carbonic acid is expelled, as will be evi- 
dent from an effervescence on the surface of the bead. 
The product when pure resembles ordinary glass, but 

880. Describe the different varieties of clay. 881. How is soluble glass 
made? 



SILICATES. 421 

dissolves in boiling water without residue. Soluble 
glass is sometimes used as a sort of varnish for render- 
ing wood or cloth fire-proof. Structures built of soft 
and friable stone may be preserved in a great measure 
from the action of the weather by a coating of this 
material. It has also been used to some extent as a 
substitute for starch or gum in stiffening fibrous sub- 
stances. It is now used in the manufacture of certain 
kinds of soap. It is asserted that the compound ob- 
tained by the addition of twenty-five pounds of liquid 
soluble glass to a hundred pounds of pure soda soap 
has a greater cleansing power than common soap. 

882. Glass. — Glass is a mixture of various silicates, 
with excess of silica, altogether destitute of crystalline 
structure, produced by fusing together the materials by 
a high and long-continued heat. The fused mass is in 
a plastic but never in a perfectly fluid condition. The 
nature and proportions of the ingredients vary accord- 
ing to the purpose for which the glass is to be used. 

883. Window Glass. — Common window glass is a 
silicate of lime and soda. To form it, chalk, 263 
soda, quartz sand and old glass are fused to- 
gether until the mass becomes fluid. The 
molten glass is then blown, by means of an 
iron tube, as soap bubbles are blown with a 
pipe. The first form of the bubble is that 
represented in the figure. The glass blower 
next contrives to lengthen out the bubble, as he blows 
it, to a larger size, and finally to blow out the end by a 

882. What is glass ? 883. Describe the manufacture of window glass. 



422 PRINCIPLES OF CHEMISTRY. 

strong blast from his lungs. It is then trimmed with a 
pair of shears, and the other end cracked off by wind- 
ing around it a thread of red hot glass. Such a thread 
is readily produced by dipping an iron rod into the pot 
of molten glass, and then withdrawing it. The bubble 
264 of glass is thus brought to the form of a 
cylinder, such as is represented in Figure 264. 
The cylinder is then cracked longitudinally, 
by letting a drop of water run down its 
length, and following it by a hot iron. It is 
subsequently reheated, opened, and flattened 
out into a sheet, which is then cut into panes 
of smaller size, if required. 

884. Glass Tubes. — To make a glass tube, a bulb is 
first blown, such as is represented in Figure 263. An 
assistant then attaches his tube to the hot bulb at the 
opposite end, and moves backward. The glass is thus 
drawn out as if it were wax, and the cavity within it is, 
elongated to a smooth and perfect bore. 

885. Glass Bottles. — Bottles and a great variety of 
other objects of glass are made by the enlargement of 
similar bulbs within a mould of the required shape. 
Bottle glass is usually made of cheaper and less pure 
materials than window glass, and contains, in addition 
to the materials before mentioned, alumina and oxides 
of iron and manganese. It owes its green color to the 
protoxide of iron. 

886. Plate Glass. — Plate glass, such as is used for 

884. How are glass tubes made ? 885. How are glass bottles made ? 
886. What is plate glass ? 



SILICATES. 423 

large mirrors and shop fronts, is a soda and lime glass 
which is cast instead of being blown. It is poured out 
of the crucible in which it is melted, upon a cast-iron 
table and rolled into sheets, which, after careful anneal- 
ing, are ground to a level surface and ultimately pol- 
ished. 

887. Crystal Glass. — This is the name given to a 
highly brilliant glass used for lenses for optical instru- 
ments, prisms, lusters and the finer qualities of cut 
glass ware. It is also called flint glass from the cir- 
cumstance that the silica used in its manufacture was 
formerly derived from pulverized flints. It is composed 
of silicate of potash and silicate of lead. The large 
proportion of lead in flint-glass gives it a high refrac- 
tive power and great brilliancy when cut, but renders 
it soft, easily fusible and liable to be acted on by many 
chemical agents. "With the addition of borax, it is 
also employed for imitations of precious stones. 

888. Bohemian Glass. — This celebrated glass is made 
mostly of silicates of potash and lime. Its hardness 
and infusibility give it a high value in laboratory ana- 
lysis. The more fusible glass which is employed in the 
manufacture of beautiful Bohemian ornamental objects 
contains also silicate of alumina. 

Crown Glass is composed of the same materials but 
in different proportions. 

889. Colored Glass. — Glass is colored and stained 
by the addition of various metallic oxides. The pecu- 

887. What is crystal glass ? 888. What is composition of Bohemian 
glass ? 889. How is glass colored ? 



424 PRINCIPLES OF CHEMISTRY. 

liar coloring effects of these substances have already- 
been mentioned, in Section 803. 

890. Enamel. — Enamel is an opaque glass, produced 
by the addition of some material which does not dis- 
solve in the fused mass. Binoxide of tin is the material 
commonly employed. Yarious tints may be imparted 
to enamel, as to ordinary glass, by the addition of small 
quantities of metallic oxides. A thin surface of enamel 
is often baked on to a metallic surface, as in the case of 
watch dials and various objects of jewelry. 

891. Annealing. — All glass to be valuable requires 
to be annealed, for when allowed to cool suddenly after 
fusion, it becomes exceedingly brittle and articles made 
from it are liable to fly to pieces upon the slightest 
touch of any substance hard enough to scratch its sur- 
face, even from a slight but sudden change of temper- 
ature, as when transferred from a cold to a warm room. 
This property is strikingly illustrated by what are called 
Huperfs drops, which are little pear-shaped masses of 
glass formed by dropping melted glass into cold water. 
These may be subjected, without breaking to consider- 
able pressure but the instant the little end of the drop 
is broken off the whole mass crumbles into powder with 
a kind of explosion. This probably arises from the 
unequal tension of the layers of glass in consequence 
of the sudden cooling of the exterior whilst the interior 
remains dilated, or even red hot. 

892. The following table will give an idea of the 

800. What is enamel ? 891. How is glass annealed ? 892. Describe the 
composition of the different kinds of glass. 



SILICATES. 



425 



relative proportions of the ingredients in the several 
kinds of glass mentioned above, viz. ; 



PLATE. 

Silica, T8 

Potassa, 2 

Soda, 13 

Lime 5 

Aluminum, 2 

Oxide of Lead, . . — 
Oxide of Iron, . . — 



BOHEMIAN. 

69 

12 

9 

10 



FEEN"T. 

...52 
.. 14 



1 
33 



BOTTLE. 

59 

2 

10 

20 

2 



OPTICAL. 

43 
12 



44 



100 100 100 100 100 

893. Eartheitwaee. — Clay is the basis of all earthen- 
ware, from the finest porcelain 
to the coarsest brick. Being 
first fashioned by moulds or other 
means into the proper form, it is 
dried, baked, and subsequently 
glazed to render it impervious to 
water. In the manufacture of 
porcelain glazing is not essential. 
Sand and chalk are added to the 
original material, and the heat is 
carried so high as to bring the 
whole mass into a semi-vitreous 
condition. This is also the case in certain kinds of 
stoneware. Porcelain is, however, commonly glazed to 
add to its beauty. 

894. Glazing. — Earthenware after its first baking is 
porous, and therefore unfit for most uses for which it is 
intended. It is subsequently covered with a thin paste 

893. What is the basis of all earthenware ? How is porcelain made ? 
894. Describe the process of glazing. 




426 PRINCIPLES OF CHEMISTRY. 

formed of the constituents of glass. Being then sub- 
jected a second time to the heat of the furnace, a thin 
glass or glaze is formed upon the surface. The glazing 
of certain wares is effected by exposure at a high tem- 
perature to vapors of common salt. A double decom- 
position ensues with the oxide of iron which the w^are 
contains, by which soda is formed. This immediately 
fuses with the silica and other materials to form the 
glaze. The chloride of iron which is formed at the 
same time passes off as vapor. A paste of pounded 
feldspar and quartz, to which borax is sometimes added, 
is employed in glazing porcelain. 

895. Porcelain Painting. — Metallic oxides form the 
basis of the pigments used in painting upon porcelain. 
The coloring effect of the different pigments is men- 
tioned in the chapter on metallic oxides. Great im- 
provements in the art of ornamenting porcelain have 
been recently effected by the discovery that the action 
of the oxygen in flame and of the products of incom- 
plete combustion modify the shade givefr to pottery by 
metallic oxides, and produce with one and the same 
material very different colors. Thus, with the oxide 
of chromium in a reducing atmosphere a blue shade is 
obtained, while with an oxidizing atmosphere a green 
color is produced showing ruby red in the light. With 
the oxide of uranium, in an oxidizing atmosphere, a 
pure yellow is brought out, and hues varying from red- 
dish brown to black in the reducing atmosphere. The 
patterns on ordinary earthenware are first printed 

895. What is said of porcelain painting ? 




BORATES. 427 

on paper, and then transferred, by pressure, to the on- 
glazed ware. The paper is afterwards removed by a 
wet sponge. 

Borates. 

896. Borax. (NaO,2BO 3 + 10Aq.) — Borax is the 
only important salt among the compounds of boracic 
acid. The salt contains two atoms of acid to 266 
one of base, and is therefore a biborate. It is 
a white soluble salt, which swells up when 
heated, in consequence of the escape of its 
water of crystallization. 

897. Preparation. — Borax is found in solution in the 
water of certain shallow lakes in India. It remains as 
an incrustation in the beds of these lakes when they 
dry up in summer. It is also prepared by the action 
of a solution of boracic acid on carbonate of soda. 

898. Borax Glass. — The light spongy mass which 
is produced on heating borax, may be melted down by 
greater heat and converted into borax glass. This glass 
has the property of dissolving metallic oxides, and re- 
ceiving from them peculiar colors, as described in a 
former paragraph. The chemist often determines the 
metal which a salt or oxide contains, by the color which 
it thus imparts to glass. The method of making the 
experiment has already been given. 

899. Soldering, Welding, etc. — Borax is employed 



896. What is borax ? 897. How is borax prepared ? 898. What is said 
of borax glass ? 899. Why is borax employed in soldering ? 



428 PRINCIPLES OF CHEMISTRY. 

in soldering metals, to keep the metallic surfaces clean. 
It does this by dissolving the coating of oxide which 
forms upon them, and forming with it a glass which is 
fluid at a high temperature, and easily pushed aside by 
the melted solder. Its use in welding iron depends on 
the same property. Iron, however rusty, may be sol- 
dered, or welded, by using as a flux the double chloride 
of zinc and ammonium which is formed by dissolving 
chloride of zinc in hydrochloric acid and adding sal- 
ammoniac. This cleans the surface of the iron and 
allows the two pieces of metal to come directly in con- 
tact with the solder or with each other. Borax is used, 
to some extent, in medicine. It is also a constituent of 
the glass called jewelers* paste, which is used in pro- 
ducing imitations of precious stones. 

Chrcmates. 

900. The chromates are prepared for use in the arts 
from the native chrome iron by fusing the ore with 
nitrate of potash ; by this treatment the chromium 
absorbs oxygen and is converted into chromic acid, 
(Cr0 3 ), which unites with the potash to form a yellow 
salt, the chromate of potash (KO,Cr0 3 .) By varying 
the process a red salt containing twice as much chro- 
mic acid as the first, the bichromate of potash, (KO, 
2Cr0 3 ) is produced. The bichromate of potash which 
crystallizes in beautiful red crystals is manufactured in 
immense quantities for use in the arts and is the source 

900. How are chromates prepared ? 




CHEO MATES. 429 

of several exceedingly valuable coloring materials and 
pigments. 

901. Chrome Yellow. (PbO,Cr0 3 ). — To prepare 
this pigment, a solution of the commercial 
bichromate of potassa is added to a solution 
of sugar of lead. A double decomposition 
ensues ; the result of which is the production 
of a beautiful yellow precipitate, known as 
chrome yellow. The precipitate is a chromate 
of lead. 

902. Chrome Orange. (2Pb0 3 Cr0 3 ).— Chrome yel- 
low may be converted into chrome orange, by digestion 
with carbonate of potassa. Cloth dyed yellow by dip- 
ping it alternately into a solution of bichromate of 
potassa and sugar of lead, is instantaneously changed 
to orange by immersion in boiling milk of lime. This 
action of the lime, as well as that of carbonate of 
potassa, depends upon its abstracting a certain portion 
of the chromic acid, leaving thereby a chromate of lead 
of different composition and color. 

903. Chrome Green. (Cr 2 3 ). — On adding sulphu- 
ric acid and a few drops of alcohol to a solution of bi- 
chromate of potassa, the solution is immediately changed 
from red to green. The alcohol has taken oxygen from 
the chromic acid, and converted it into oxide, which 
remains in solution, as a soluble sulphate. Part of the 
sulphuric acid has at the same time combined with the 



901. How is chrome yellow prepared ? 902. How is chrome yellow 
converted into chrome orange ? 903. Describe the preparation of oxide 
of chromium. 



430 PRINCIPLES OF CHEMISTRY. 

potassa, to form sulphate of potassa. It is to the pres- 
ence of the sulphate of chromium in solution that the 
color of the liquid is due. By adding an alkali to the 
solution, a green precipitate of the hydrated oxide is 
produced. This oxide forms a kind of " chrome green." 
Commercial chrome green is a mixture of Prussian 
blue and chrome yellow. 

Manganates. 

904. Manganate of Potash. — Chamelon Mineral. 
(KO,Mn0 3 ) — By fusion with nitre, the black oxide of 
manganese may be still further oxidized, and converted 
into an acid. The new acid at the same time combines 
with the potassa of the nitre to form manganate of 
potassa. This salt has been called chameleon mineral, 
from the spontaneous change of color which takes place 
in its solutions. 

905. Preparation. — The experiment may be made 
by filling a pipe-stem with a mixture of the materials, 
and thrusting it into burning coals. It may be made 
on a still smaller scale before the blow-pipe, using a 
broken pipe-bowl to support the materials. The com- 
pound dissolves in water, forming a green solution, 
which on standing is gradually changed to a beautiful 
red. 

906. Explanation. — The addition of a few drops of 
sulphuric acid, produces the above-mentioned change 
instantaneously. This acid combines with the potassa, 

904. What is chameleon mineral? 905. How is chameleon mineral 
prepared ? 906. Explain the action of sulphuric acid upon it. 



PHOTOGRAPHY. 431 

setting the manganic at liberty. One portion of man- 
ganic acid then appropriates part of the oxygen of the 
other part, and converts itself into permanganic acid, 
(HO,Mn 2 7 ), which still remains combined with potassa, 
imparting the red color to the solution. The deoxy- 
dized portion of the acid precipitates, at the same time, 
as binoxide of manganese. 

907. Permanganate of Potash. * (KO,Mn 2 7 ). — 
By evaporating the red or purple solution, mentioned 
in the preceding paragraph, deep ruby-colored crystals 
of permanganate of potassa are obtained, which are 
soluble in 16 times their weight of water. The solu- 
tion of this salt is now much employed in volumetric 
analysis. It readily parts with its oxygen to organic 
matter and deoxidizing bodies generally, by which it 
loses its color, and brown hydrated peroxide of manga- 
nese is deposited. A standard solution of permanga- 
nate has been employed for determining the amount of 
organic matter in air and water. A solution of this 
salt has been much used for the removal of foul efflu- 
via in sick rooms. It is also applied for the same pur- 
pose to cancerous and other offensive ulcers. 

Photography. 

908. Photography is the art of producing pictures 
by the action of light. It depends upon the chemical 
changes which the salts of silver undergo when exposed 
to light. Solutions of gold and various other salts un- 

907. What is permanganate of potash ? For what purposes is it used ? 
908. On what does the art of photography depend ? 



432 PRINCIPLES OF CHEMISTRY 

dergo chemical changes by the action of light, but none 
are so well adapted to the photographic art as the salts 
of silver which are almost exclusively employed for 
this purpose. All the salts of silver are more or less 
affected by light. In some instances they undergo a 
visible change, being rendered dark in proportion to 
the intensity of the light and the length of exposure. 
This is well seen in the white chloride of silver when 
ip a humid state ; and in the nitrate and ammonio- 
nitrate in contact with organic matter. The iodide and 
bromide of silver do not darken by exposure to light, 
but they undergo instantaneously a remarkable molec- 
ular change which renders them especially adapted for 
photography. 

909. The Daguerreotype may be regarded as a 
painting in mercury upon a silver surface. The em- 
ployment of mercury is preceded by what may be called 
an invisible painting upon a delicate film of the iodide 
or bromide of silver upon the surface of the silver plate. 
This is accomplished, like the production of an image 
in a mirror, by mere presentation of the picture, or 
other object to be copied, before the prepared plate. 
The mercury, afterward used in the form of vapor, 
adheres to the plate, and forms its white amalgam, just 
in proportion to the lights and shades of the previous 
image thrown upon the plate. 

910. The Daguerreotype Process. — In order to 
prepare the plate for what has above been called the 

909. Explain the daguerreotype. 910. Describe the process of taking 
daguerreotypes. 



PHOTOGRAPHY. 433 

invisible painting, it is exposed to vapors of iodine, and 
thereby covered with a coating of iodide of silver.* 
A picture or face to be copied being presented before 
the prepared plate, the light which proceeds from it 
acts chemically npon the iodide of silver. It decom- 
poses it, to a certain extent, and separates the iodine, 
thus opening the way for the mercurial vapor which is 
afterward to be employed. The light has this effect 
just in proportion to its intensity. That which pro- 
ceeds from the lighter portions of the face, or dress, has 
most effect ; that from the black portions, none at all, 
and that from the intermediate shades, an effect in 
exact proportion to their brightness. When the plate 
is afterward exposed to the action of the mercurial 
vapors, they find their way to the silver surface and 
paint it white, just in proportion as this chemical effect 
upon the iodine has been produced, and the way has 
been opened for their admission. The darker portions 
of the plate are pure silver. They appear dark in con- 
trast with the white amalgam.f 

911. Use of the Lens. — In taking daguerreotypes, 
a lens is placed between the object to be copied and the 
plate, in order that an image may be formed on the 
silver surface. Such an image is analogous to that 

911. What is the object of the lens ? 



* Bromide and chloride of iodine are employed to give additional sensitiveness to 
the plate. The iodide is thus made to contain a portion of bromide and chloride 
of silver. 

t The art of taking portraits from the life by the Daguerreotype process, was 
invented by Dr. J. W. Draper, of the N. Y. University. 



434 PRINCIPLES OF CHEMISTRY. 

formed on the retina of the eye. The image is com- 
monly made smaller than the object. "Where this is the 
case, the rays are used in a concentrated condition, and 
their effect is proportionally increased. 

912. Chemical Action of Light. — The chemical 
action of light, on which the production of daguerreo- 
types depends, is one of the most interesting and re- 
markable of chemical phenomena. The rays of the 
sun are so subtle that they pass through solid crystal 
and leave no trace of their passage. Yet with them 
comes a power that can overcome the strongest chemi- 
cal affinities, and resolve the compounds which it has 
produced into their original elements. This power 
resides in what are called the chemical, actinic, or ti- 
thonic rays. These are mingled, under ordinary circum- 
stances, with those of light, but are capable of separa- 
tion by certain media. 

913. Photographs. — Pictures produced through the 

agency of light, whether upon 
silver or paper, are, properly, 
photographs or light pictures j 
the name, however, is especially 
appropriated to pictures pro- 
duced by the agency of light upon paper prepared for 
the purpose. The production of these pictures em- 
braces two distinct processes. First the production of 
a negative, or a picture in which the dark parts of the 
object are light in the picture and the light parts dark, 

912. What is said of the chemical action of light ? What rays possess 
this power? 913. What are photographs? 



HXY 



PHOTOGRAPHY. 435 

like the letters H, X, Y, in figure 268. Second, the 
production from the negative of a picture called a 
positive in which all the parts of the object possess their 
appropriate relations of light and shade. In these 
pictures the colors are seldom the same as in the real 
object. 

914. Negative Pictures are prepared upon glass 
covered with a thin film of collodion. The collodion 
used for thi3 purpose is prepared by adding to every 
ounce of plain collodion 3 grains of iodide of potassium^ 
2 grains of bromide of potassium and 6 grains of sal- 
ammoniac. The collodion thus prepared is poured over 
the surface of the glass and allowed to harden, when it 
is immersed in a bath c ? nitrate of silver. The silver 
bath contains 49 grains of nitrate of silver to an ounce 
of distilled water, and to this is added as much iodide 
of silver as the solution of nitrate will dissolve. The 
glass plate coated on one side with the prepared collo- 
dion is immersed for a few minutes in this silver bath 
when it is ready for use. The plate is then placed in 
the camera and the image of the object to be copied is 
thrown upon it as shown in figure 269, the light from 
all other sources except the object being carefully ex- 
cluded. The camera consists of a rectangular wooden 
box as shown in the figure, to one face of which is 
attached a tube, bearing a lens, which forms the image. 
The opposite face of the box consists of a sliding drawer, 
holding a plate of ground glass, upon which the image 
is thrown, and by drawing it out, or sliding it in, the 

914. How are negative pictures produced ? 



436 



PRINCIPLES OF CHEMISTRY. 



picture may be rendered distinct upon the glass. When 
"the image is clearly defined, the plate of glass is re- 




moved, and the collodion plate is introduced as above 
mentioned and exposed for a few seconds to the light 
of the image. The plate is then removed and in a 
dark room it is washed with a developing fluid which 
removes the salt of silver from the parts not acted on 
by the light and brings out the negative picture as above 
described. A common developing fluid is made by 
mixing 2 ounces of sulphate of iron, 6 drops sulphuric 
acid, 3 drachms acetic acid and half an ounce of alco- 
hol with a quart of water. The distinctness of the 



PHOTOGRAPHY. 437 

picture is afterwards increased by immersing in the to- 
ning hath / consisting of 3 quarts of water, 1 pound hypo- 
sulphate of soda, 3.t ounces nitrate of silver changed 
into chloride and washed, and 5 grains chloride of gold. 
After these processes are completed the picture is per- 
manently fixed upon the plate by means of transparent 
varnish. 

915. Ambrotypes are negative pictures placed upon 
a background of black varnish or other dark substance. 
They may be made upon glass and backed with black 
cement or upon plates of japaned iron or leather. 

916. Photographic Printing ; Positive Pictures. — 
Positive pictures are printed from negatives with light 
and shade reversed on sensitive paper exposed to sun- 
light covered by the negative picture. Sensitive paper 
is prepared by immersion in a solution of common salt, 
80 grains of salt to a quart of water, and afterwards in 
a solution of ammonio-nitrate of silver. It is then 
dried in the shade when it is ready for use. A suitable 
sensitizing solution may be prepared as follows : Dis- 
solve an ounce and a quarter of nitrate of silver in a 
pint of distilled water, put three ounces of the solution 
in a separate bottle and to the remainder add aqua 
ammonia chemically pure, drop by drop, until the silver 
is first deposited and then redissolved, pour in the three 
ounces which had been reserved when a slight deposit 
will again appear, filter the liquid and it is fit for use. 
Immerse paper of the finest quality two or three times 



915. What are ambrotypes ? 916. How are positive pictures printed 
from negatives ? 



438 PRINCIPLES OF CHEMISTRY. 

in this fluid and place it between blotting paper to re- 
move the superfluous liquid, dry the paper in the dark 
and it is ready for use. It is sufficient to sensitize one 
side of the paper only. 

The negative plate is placed over the paper on the 
sensitive side and exposed for a few minutes to the 
direct rays of the sun. The positive picture is thus 
produced with light and shade in their natural rela- 
tions. The chloride of silver on the paper is partially 
decomposed. A new substance, of darker color, is then 
produced ; whether a lower chloride of different shade, 
or a mixture of metal and chloride, or a compound of 
oxide and chloride, is not very certainly known. 

917. Fixing the Picture. — If nothing more was 
done the whole surface of the paper would soon be 
blackened and the picture would disappear. The pic- 
ture is fixed by washing the paper in a solution of 
hyposulphite of soda which removes the chloride of 
silver which has not been acted on by the light, while 
that portion which has been changed by light remains 
as the coloring matter of the permanent picture. 

Note. — The details of all the processes described in sections 915, 916 and 
91Y are considerably varied by different artists. 

918. Anastatic Printing. — This name is given to a 
process by which any kind of printed matter may itself 
be converted into a plate from which new copies may 
be printed. The paper containing printed matter or 
other designs is moistened with dilute nitric acid but 

917. How is the picture rendered permanent ? 928. Describe briefly 
the process of anastatic printing. 



PHOTOGRAPHY. 439 

the ink containing oil is not moistened. The paper is 
then laid upon a sheet of polished zinc and submitted 
to pressure by which a portion of the ink adheres to 
the zinc and protects the zinc from the action of the 
acid. When the acid in the paper touches the zinc it 
corrodes it and forms a surface to which ink will not 
adhere. The paper is then removed and the plate is 
washed with gum water which wets the corroded sur- 
face and leaves the inked surface untouched. The zinc 
plate is then used like an ordinary lithographic stone. 
When the inked roller is passed over it, the ink only 
adheres to the design, from which an impression may 
then be taken by the ordinary process. 

919. Counterfeiting. — Bank notes may be counter- 
feited either by photography or by the anastatic pro- 
cess. Great apprehension has been felt lest they 
should render the use of paper money entirely insecure. 
An effectual means of protection against such counter- 
feiting has recently been devised.* Copying by the 
anastatic process, obviously depends upon the absence 
of oil from the back ground of the picture. The em- 
ployment of an oil tint, instead of blank paper, for the 
back ground, is therefore a perfect security against it. 
Counterfeiting by the photographic process depends on 
the fact that the light which falls on a picture is inter- 
cepted by the dark letters. If they are printed in a 
transparent blue, the chemical rays are permitted to 

919. What is said of counterfeiting by the above process ? 



* Seropyan's patent. 



440 PRINCIPLES OF CHEMISTRY. 

pass through the printed as well as the imprinted por- 
tions. A copy with the contrasts of the original pic- 
ture is thereby rendered impossible. By printing with 
blue ink, on a back ground of some other color, both of 
the securities against counterfeiting above mentioned 
are combined. The green colors upon United States 
treasury notes are another device to prevent counter- 
feiting. Recent IT. S. bonds have the denomination 
printed in a gilt device underneath the engraving which 
cannot be removed and cannot be copied by photogra- 
phy or by any other known process. 



PART IV. 

ORGANIC CHEMISTRY. 



CHAPTER I 

GENERAL VIEWS 

920. Definition. — Organic chemistry is that division 
of the science which treats of substances of vegetable and 
animal origin. Wood, starch, gums and resins; the 
juices, coloring matters, and fragrant principles of 
plants ; the blood and flesh of animals ; all come under 
its consideration. The process of germination, in which 
the plant first becomes a living thing; the processes 
of decay and putrefaction in which it returns to the 
earth and atmosphere, are also to be treated under this 
division of the subject. Most organic forms of matter 
experience peculiar changes, and are converted into new 
substances by natural or chemical means. The pro- 
ducts of such transformations — with the exception of 
a few, such as water, carbonic acid and some other sub- 
stances, which also exist ready formed in nature — be- 
long to organic chemistry. 

920. Of what does organic chemistry treat ? 



442 ORGANIC CHEMISTRY. 

921. Elements in Organic Bodies few. — Organic 
products differ remarkably from bodies which belong 
to the mineral or inorganic kingdom; and in many 
cases they may at once be distinguished by their exter- 
nal appearance. A striking peculiarity of their chemi- 
cal character is the limited number of elements that 
enter into their composition. Some organic substances 
contain carbon and hydrogen only. A greater number 
are constituted of three elements, carbon, hydrogen and 
oxygen. Some contain in addition to these three, ni- 
trogen ; while a few have, besides these, a minute pro- 
portion of sulphur and phosphorus, with certain earthy 
and saline matters. The presence of carbon is so uni- 
form in organic substances that generally an unknown 
body may be determined to be of organic origin by its 
becoming charred and blackened when heated without 
a full supply of air. 

922. Variety of Organic Matter. — Though the 
number of elements entering into the composition of 
organic bodies is so limited, it may not be correctly 
inferred that the number of bodies is small. The re- 
verse is true, for by a sort of fermentation the variety 
of distinct organic substances is almost without limit. 
By the arrangement of these different elements in dif- 
ferent ways and in different proportions a host of 
organic forms is produced, presenting characters the 
most diverse and most variable. Sugar contains the 
same elements as vinegar. All the components of 

921. What are the elements of organic bodies ? 922. What is said of 
the variety of organic matter? 



MATERIALS OF ORGANIC GROWTH. 443 

strychnia are found in a crust of bread. Every color 
of every dye, every flavor of every sweet or bitter herb, 
every gum and every resin, is a distinct organic sub- 
stance, though each of these may be made up of the 
same elements. In the animal body there is scarcely 
less variety. The number of substances that fall into 
the province of organic chemistry is thus immense. 

923. Materials of Organic Growth. — With the 
exception of the small proportion of mineral matter, 
which is derived from the earth, the materials out of 
which all animal and vegetable substances are formed 
are but few in number. In carbonic acid, water, and 
ammonia, and these derived partly from the air and 
partly from the earth, the plant finds the carbon, hy- 
drogen, oxygen and nitrogen out of which it is con- 
structed. 

924. Conversion of the Materials.— A vital prin- 
ciple slumbers within the seed, which in germination 
wakes into life. Calling to its aid the light and warmth 
of the sun, it weaves out of the scanty inorganic mate- 
rials which have just been mentioned all the varied 
forms of vegetable matter. Among the materials one 
is a tasteless solid; the rest are tasteless gases. Yet 
sweet, sour and bitter flavors result from their combi- 
nations, with all the boundless variety of the organic 
world. 

925. Instability of Organic Products.- — Another 



923. What are the materials of organic growth ? 924. What causes 
the changes of organic materials ? 925. What is said of the stability of 
organic products ? 



444 ORGANIC CHEMISTRY. 

peculiarity which characterizes organic products, though 
not so universal as that of the limited number of ele- 
ments, is their instability. "While a few remain perma- 
nent under ordinary circumstances, the larger number 
have a tendency to change, to decay, and to fall back to 
the materials out of which the plant constructed them. 
During this decay new compounds are produced adding 
still to the number of products which plants have 
formed during their growth. Chemical agents often 
assist in promoting changes, and the number of sub- 
stances becomes yet more varied. The result of these 
changes is usually the production of substances of more 
simple composition, which are one step nearer the car- 
bonic acid, water and ammonia from which they came 
and to which they will ultimately return. 

926. Identity of Composition. — Attention has been 
called to the fact that organic substances have a re- 
markable identity of composition, the same elements 
in different proportions forming compounds of remark- 
ably diverse character. Stranger than this, and at the 
first view incredible, is the fact that many organic sub- 
stances, differing widely in properties, are precisely the 
same in their composition; not alone containing the 
same elements but containing them in precisely the 
same proportion. The sugar which sweet milk fur- 
nishes and the acid which exists in the sour, contain 
identically the same proportions of the same constitu- 
ents. The oils of turpentine, lemon and pepper, so 

926. What is said of identity of composition ? 



ISOMERISM. 445 

different in tlieir taste, contain an equal quantity of 
carbon and hydrogen, without the addition of any third 
substance to either to account for the difference. Chem- 
ical investigation has thus brought us to results as strange 
as the dream of the alchemist, who believed that lead 
might be converted into silver, and copper into gold. 
All such substances possessing the same composition 
with different properties are called isomeric bodies — a 
term signifying their similarity of composition. 

927. Isomerism. — The examples instanced serve to 
show that mere identity of ultimate composition is not 
sufficient to produce identity of chemical character or 
properties. At a loss for any other way of accounting 
for such difference of properties we are compelled to 
believe that it is because of difference of atomic ar- 
rangement. We have seen in the case of iodide of 
mercury, mentioned in Section 826, that a mere touch 
will produce motion and re-arrangement of its atoms 
in smaller groups, and at the same time change the 
color of the compound from yellow to red. There 
are various forms of isomerism ; in some cases we have 
no clue to the probable difference of molecular arrange- 
ment ; in others there is every reason to suppose that 
the arrangement of the elementary atoms is on a totally 
different plan in the two or more bodies compared. 
Now the molecule of lactic acid, although containing 
the same relative proportion of all the constituents, is 
smaller than the molecule of sugar of milk. It con- 

327. What is meant by isomerism ? 



446 ORGANIC CHEMISTRY. 

sists of six atoms of carbon, six of hydrogen, and six 
of oxygen, (C 6 H c 6 ). The molecule of sugar of milk 
contains twenty-four of each (C24H24O24) and can there- 
fore furnish material to make four of acid as it does in 
the souring of milk. And we may suppose that the 
change from sweet to sour is owing to this subdivision 
of the molecules. 

928. Different Forms of Isomerism. — In some 
cases the difference of properties of bodies which con- 
tain equal percentages of their constituents, may be 
simply explained upon the supposition that the state of 
condensation of those elements is different. Methy- 
line, a gaseous body, is regarded as being made up of 
two atoms of carbon and tw T o of hydrogen (C 2 H 2 ) ; 
ethylene or defiant gas of four of carbon and four of 
hydrogen (C 4 H 4 ); and tetrylene or oil gas, of eight of 
carbon and eight of hydrogen (C 8 H 8 ). The density of 
these bodies is proportioned to the number of atoms 
they are here represented to contain. Bodies supposed 
to be thus constituted are termed polymeric. 

There are other cases of identical composition in 
which there is no difference whatever in the size of the 
molecule or the number of atoms which enter into its 
composition. This is the case with the oils of turpen- 
tine, lemon and pepper. The molecules of each are 
composed, not alone of the same proportion of the ele- 
ments which enter into its composition, but there is 
reason to believe of the same number of atoms of each. 

923. What varieties of isomerism are mentioned? 



CHANGE OF COMPOUNDS. 



447 



Isomeric compounds of this kind, the equivalent num- 
bers of which are identical, are said to be metameric. 
In these we are compelled to look for the difference 
which shall account for their peculiar property in a dif- 
ferent arrangement of atoms inside of the molecules 
l themselves. In illustration we may conceive of several 
bodies the composition of which is expressed by the 
formula C 6 H 5 5 ; and the atoms grouped somewhat as 
represented in the accompanying figures. 

270 271 272 






929. Change and Multiplication of Compounds. 
— Many organic substances when removed from the 
influence of the vital principle and exposed freely to 
the air, begin at once to change ; begin to decay. The 
gradual decay of organic compounds is chiefly a pro- 
cess of spontaneous oxidation ; for decay is in reality 
only a slow combustion. The body is attacked by the 
oxygen of the air, and burned, and destroyed, though 
so gradually as to produce no sensible elevation of tem- 
perature. Some substances which do not thus spon- 
taneously change have the oxidizing action induced by 
contact with a body which is itself undergoing slow 



929. How are organic compounds multiplied ? 



448 ORGANIC CHEMISTRY. 

oxidation. The action of heat exalts the attraction 
of oxygen for hydrogen and carbon, and we see the 
almost universal destruction of organic substances at a 
high temperature. In ordinary combustion but few 
compounds are obtained, the change being speedily 
effected and bodies, such as are found in the inorganic 
world, produced. But when the common process is 
interfered with by shutting off contact with the air, as 
in destructive distillation, a host of new products, vary- 
ing according to the temperature and other attending 
circumstances, is the result. Some of the most impor- 
tant of these organic compounds will be noticed in suc- 
ceeding paragraphs. 

930. The chemist in examining the composition of 
organic bodies and tracing their relations to other com- 
pounds, calls to his assistance a variety of agents and 
by their aid produces metamorphoses, the different 
steps of which he can trace. Sometimes changes are 
effected by imitating nature and the method of oxida- 
tion is used. The organic body is brought in contact 
with some powerful oxidizing agent, such as nitric acid, 
chromic acid or a mixture of sulphuric acid and black 
oxide of manganese, under the influence of which, by 
a transfer of the oxygen, the desired change is accom- 
plished. Sometimes the reverse process of reduction is 
adopted, at other times a method of displacement or sub- 
stitution, by which the atoms or molecules of one body 
are made to take the place of those of a different kind 

930. How does the chemist examine organic bodies ? 



SUBSTITUTION OF ELEMENTS. 449 

in another body, is used. From a compound a certain 
number of atoms of hydrogen may be removed and an 
equal number of atoms of another element may be sub- 
stituted. Even compound substances, as the molecule 
of peroxide of nitrogen, (N0 4 ) may thus displace the 
atom of hydrogen. 

931. Substitution. — The study of the action of such 
substances as may replace others in combination has led 
to a knowledge of unlooked-for facts. Strange as it 
may appear, one element may take the place of another, 
and in many cases the character of the original body 
will be but slightly changed, even though the new sub- 
stance introduced be wholly different in chemical char- 
acter from the one that has been displaced. Hydrogen 
may be displaced by chlorine, a body as widely differ- 
ent from it as anything which nature affords. The 

mode of action consists in the removal of the hvdro- 

t/ 

gen, or more rarely some other element of the organic 
substance, and the substitution of some element or 
compound, equivalent for equivalent, without destruc- 
tion of the primitive constitution of the original com- 
pound. By such substitution ordinary hydrated acetic 
acid, (HO,C4H 3 3 ), may have its hydrogen displaced by 
chlorine, giving rise to trichloracetic acid, (H0,C 4 C1 3 3 ), 
a stable substance of strong acid character, remarkably 
analogous to the acid from which it was formed. From 
this again, by withdrawing the chlorine and restoring the 
hydrogen, the original acetic acid is reproduced. In the 

931. What is said of substitution 9 



450 ORGANIC CHEMISTRY. 

conversion of acetic acid into trichloracetic acid one 
element appears to have taken the place of another with- 
out disturbing the relative positions of the other con- 
stituents ; as we may conceive a brick may be removed 
from an edifice whilst its place is supplied by a block 
of wood, or stone, or metal, without altering the form 
or symmetry of the structure. 

932. Types. — The last example will serve as an illus- 
tration of the doctrine of chemical types and substitu- 
tion, which certain chemists have endeavored to extend 
to all organic bodies. It has been asserted that the 
properties of these bodies depend solely upon arrange- 
ment without any reference to the nature of the ele- 
ments combined. The fact is, that while there are 
many cases of such substitution without essential change 
of properties, it is always attended by more or less 
modification of the original substance. The properties 
of compounds are therefore to be regarded as depend- 
ing neither upon the nature nor arrangement of atoms 
alone, but upon both causes combined. The type is the 
group which remains permanent while the individual 
atoms which compose it are changed. 

933. Compound Radicles. — -In organic chemistry 
radicles are represented by simple substances which 
enter into combination with oxygen, chlorine and that 
class of elements, forming a class of compounds. Thus 
sulphur is the radicle of sulphurous acid, (S0 2 ,) and sul- 
phuric acid, (S0 3 ). Many organic bodies, although com- 
pounds, comport themselves as though they were ele- 

932. What are organic types ? 933. What are compound radicles ? 



COMPOUND RADICLES. 451 

mentary substances. Some of these correspond in 
properties to metals, forming oxides, chlorides and salts, 
like true metals. Others resemble the metalloids. 
Each being organic, and like a metalloid, the root of a 
whole series of compounds is called an organic radicle, 
and as the organic substances above referred to are 
composed of different elements, they are called com- 
pound radicles. 

934. Illustration. — A molecule of ordinary ether is 
composed of four atoms of carbon, five of hydrogen 
and one of oxygen, (C 4 H 5 0). But the carbon and hy- 
drogen are grouped together forming a compound radi- 
cle called ethyl. (C 4 H 5 ,) is combined with the oxygen to 
form ether or the oxide of ethyl. Al- 273 
cohol, as illustrated in the figure, is 
the hydrated oxide of this radicle. 
Ethyl itself may be prepared indi- ® ®®@@ © 
rectly from the oxide as potassium is obtained from 
potassa or oxide of potassium, although by a different 
process. 

935. Composition and Analogies of Compound Rad- 
icles. — Compound radicles, compound bodies which 
act like elements, may consist of two, three or more 
elements. They are often represented by symbols as 
in case of elements. Cyanogen, one of the simplest, 
as well as the earliest discovered, is composed of two 
atoms of carbon and one of nitrogen, (C s N=Cy.) In 
its chemical properties it is analogous to chlorine. In 

934. How is this subject illustrated? 935. What is said of the compo- 
sition and analogy of compound radicles ? 




452 ORGANIC CHEMISTRY. 

kakodyl, which has the character of a metal, there 
are three elements and its composition is expressed by 
C 4 H 6 As = Kd. In the cyanide of kakodyl, (C 4 H 6 Asi- 
C 2 N=KdCy), we have an instance of two compound 
radicles combining like elements. Ethyl, (C 4 H 5 = Et) 
the organic radicle mentioned in a preceding para- 
graph, discharges functions in the compounds of which 
it is the root analogous to potassium in its salts. We 
may compare the composition of some of these bodies. 



KO 


EtO. 


KO,HO 


EtO,HO. 


KC1 


EtCl. 


KO,SOs 


EtO,S0 8 . 


KI 


EtI. 


KO,N0 3 


EtO,N0 3 . 


KS 


EtS. 


KO,N05 


EtO,N0 5 . 



936. Radicles not Isolated. — The larger part of 
the organic radicles have not yet been isolated. They 
are only known in their compounds, yet the probability 
of their existence is so great that most chemists do not 
hesitate to give them names and places among chemi- 
cal bodies. Absolute demonstration is needed in the 
form of complete isolation, that the true classification 
of groups may . be assured, and the progress of the 
study of organic chemistry facilitated, which has been 
so greatly accelerated by the discovery of those already 
known. 

937. Substitution Compounds. — It was stated in a 
previous paragraph that there are many cases of sub- 
stitution of elements for each other without material 
change of properties. Certain cases of substitution of 

936. What is said of radicles not isolated ? 937. What are substitution 
compounds ? 



HOMOLOGOUS SERIES. 453 

compound radicles for the elements remain to be no- 
ticed. Theoretically considered they are among the 
most important discoveries which have for years been 
made in organic chemistry. Ammonia, as the student 
is already informed, is a volatile base whose molecules 
consist of one atom of nitrogen and three atoms of hy- 
drogen, (NH 3 ). For one of these atoms of hydrogen a 
molecule of the radical ethyl (C 4 H 5 ) may be substituted 
without very materially affecting its properties. The 
new ammonia thus formed is like the first, a volatile 
base resembling the first so nearly in odor that it must 
have been repeatedly mistaken for it when accidentally 
produced. It is, however, a liquid at ordinary temper- 
atures. This body has received the name of ethylamine 
or ethylia, and its composition expressed by the formula, 
(NH, (C 4 H 5 )). Diethylia (NH(C 4 H 6 ) 9 ) is another body 
produced by the substitution of two molecules of ethyl 
for two atoms of hydrogen. Triethylia (S"(C 4 H 5 ) u ) is 
a third in which all the original atoms of hydrogen 
have been displaced. By a similar substitution of hy- 
drogen in ammonia by the radicle methyl, another 
series is produced. Other radicles yield other series. 
Substitutions may even exist in the substituting radi- 
cles. All these bodies retain the type of ammonia, and 
all of them have basic properties. Many of them are 
strikingly similar to ammonia in odor and other prop- 
erties. 

938. Homologous Series. — Certain of the compound 
radicles sustain to each other a curious numerical rela- 

938. What are homologous series ? 



454 ORGANIC CHEMISTRY. 

tion. They form a series in arithmetical progression 
differing from each other in composition by a common 
difference. In the series to which ethyl belongs, the 
common difference is two atoms of carbon and two of 
hydrogen, (C 2 H 2 ). Methyl, the radicle of wood-spirit 
begins the list with two atoms of carbon and three of 
hydrogen, (C 2 H 3 ). Ethyl follows — its composition be- 
ing expressed by the addition of the common difference 
to the last — (C 2 H 3 + C 2 H 2 =: C 4 H 5 ). High in the series is 
melissyl, with a composition expressed by C 60 H 61 . Each 
of these radicles has, like ethyl, its own oxide or ether, 
its hydrated oxide or alcohol ; also its aldehyde and its 
acid. A series of radicles — ethers, alcohols, aldehydes and 
acids, each in arithmetical progression, is thus produced. 
Such series are called homologous. The composition of 
a few of the lower numbers of some of the most com- 
mon groups is expressed below. 



ADICLES. 


ETHERS. 


ALCOHOLS. 


ALDEHYDES. 


ACIDS. 


C2H3 


C 2 H 3 


C 2 H 4 2 


C 2 H 2 2 


C2-EI2O4 


C4H5 


C4H5O 


C 4 H 6 2 


C 4 H 4 2 


C 4 H 4 4 


O a H 7 


6 H 7 


C 6 H 8 3 


C 6 H 6 2 


C 6 ET 6 4 


C 8 H9 


C 8 H 9 


CVEi\o0 2 


C 8 H 8 2 


C 8 H 8 4 


CioH u 


C 10 H u O 


Ci H 12 O 2 


CioH 10 2 


C 10 H 10 O 



939. There are numerous gaps in most of the series, 
but the law of their progression has been so well estab- 
lished that no doubt can exist as to the probable pro- 
duction of the missing numbers ; and as many of the 
gaps have been filled since the existence of these homolo- 

939. Are homologous series always complete ? 



CRYSTALLOIDS AND COLLOIDS. 455 

gous series was first pointed out, it may be expected 
that before long these series will be complete. 

940. Progression of Properties. — The properties 
of the various members belonging to the homologous 
series gradually change as we ascend in the series. The 
most characteristic alteration is the diminution of vola- 
tility. The lower members of the alcohol series are 
highly volatile liquids ; the later are solids at ordinary 
temperatures. The extreme terms of the series of acids 
compared, show a similar difference ; formic acid being 
a volatile liquid w T hich requires cooling below 32° in 
order to render it solid, whilst mellissic acid requires a 
temperature of 192° for its fusion. This change is 
gradual : for each increment of C 2 H 2 the boiling tem- 
perature of the homologous acids rises on an average 
about 36°F. The density of the vapors increases by a 
similar law. It is thus possible to predict with accu- 
racy the boiling point and density of vapors in members 
of the series which have not yet been discovered. 

Crystalloid and Colloid Forms of Matter. 

941. DlFFUSIBILITY OF CRYSTALLOID SUBSTANCES. 

We have already seen (Section 763), that most inorganic 
substances, in passing from the fluid to the solid state, 
have a tendency to assume definite and regular forms 
called crystals. It is further to be noticed that when 
crystalline substances enter into solution in water or 

940. What is said of the progression of properties ? 941. W r hat is said 
of the diflfusibility of crystalloid substances ? 



456 ORGANIC CHEMISTRY. 

watery fluids they are rapidly diffused through the mass 
of water with which they are mingled ; but the rapidity 
of diffusion varies considerably for different substances. 
When this class of substances are in a state of solution, 
they pass readily through membranes or porous parti- 
tions which water can penetrate. This power of pass- 
ing in solution through membranes is called osmose, 
and it differs greatly in amount for different substan- 
ces, and varies with the nature of the membrane itself. 
Thus if a bladder is filled with alcohol and immersed in 
water, the alcohol will pass through the bladder into 
the water and be mingled with it, at the same time 
some of the water will pass into the bladder, but more 
slowly than the alcohol flows out. If, however, the 
alcohol is confined in a sac made of the lining mem- 
brane of the gizzard of a chicken, the water will flow 
in faster than the alcohol will pass out. 

Crystalline substances in a state of solution are held 
by the solvent with a certain degree of force which 
diminishes the volatility of the fluid. The solution is 
generally free from viscosity and is always sapid. The 
chemical reactions of such substances are energetic and 
quickly effected. 

942. Colloid Substances. — In the organic kingdom 
we find many substances of a gelatinous form, which 
have little if any tendency to crystallize, and which on 
being separated from water assume a vitreous structure. 
These substances, which may be typified by animal 
gelatine, have received the name of colloids. While 

943. What are the properties of colloid substance* ? 



CRYSTALLOIDS AND COLLOIDS. 457 

the crystalline form is the more common among inor- 
ganic bodies, the colloid is the more common form of 
organic matter; yet some organic bodies have the crys- 
talline and some inorganic bodies the colloid form. 
The planes and angles of the crystal, with its hardness 
and brittleness, are replaced in the colloid by rounded 
outlines with more or less softness and toughness of 
texture. Water of crystallization is represented by 
water of gelatination. Colloids are held in solution by 
a feeble power, and they have little effect on the vola- 
tility of the solvent. The solution of colloids has 
always a certain degree of viscosity or gumminess when 
concentrated. They appear to be insipid, or wholly 
tasteless, unless when they undergo decomposition upon 
the palate and give rise to sapid crystalloids. Their 
solid hydrates are gelatinous bodies. They are united 
to water with a force of low intensity ; and such is the 
character of the combinations in general between a 
colloid and a crystalloid, even although the latter may 
be a powerful reagent in its own class, such as an acid 
or an alkali. In their chemical reactions, the crystal- 
loidal appears as the energetic form and the colloidal 
the inert form of matter. Among the colloids rank 
hydrated silicic acid (§ 508) and a number of soluble 
hydrated metallic peroxides, of which little has hitherto 
been known ; also starch, the vegetable gums, dextrin, 
tannin, albumen, and vegetable and animal extractive 
matters. 

943. Colloids the Basis of Oeganization, — The 

943. How are colloids related to organization ? 



458 ORGANIC CHEMISTRY 

peculiar structure and chemical indifference of colloids 
appear to adapt them to act as the basis of organic 
bodies of which they become the plastic elements. 
Although chemically inert in the ordinary sense, col- 
loids possess a comparative activity of their own arising 
out of their physical properties. The rigidity of the 
crystalline structure shuts out external impressions, but 
the softness of the gelatinous colloid partakes of fluidity, 
and enables the colloid to become a medium for liquid 
diffusion, like water itself. The same penetrability 
appears to take the form of a capacity for cementation 
in such colloids as can exist at a high temperature. 
Hence a wide sensibility of colloids to external agents. 
Another eminent characteristic of colloids is their mu- 
tability. Their existence is a continued metastasis. A 
colloid may be compared in this respect to water while 
existing liquid at a temperature below its freezing point, 
or to a supersaturated saline solution. The solution of 
the hydrated silicic acid, for instance, is easily obtained 
in a state of purity, (§ 508), but cannot be preserved. 
It may remain fluid for days or weeks in a sealed tube, 
but it is sure to gelatinize at last. Nor does the change 
appear to stop at that point ; for the mineral forms of 
silicic acid deposited from water, such as flint, are found 
to have passed, during the geological ages of their ex- 
istence from the vitreous or colloidal into the crystalline 
condition. The colloidal is in fact a dynamical form 
of matter ; the crystalloidal being a statical condition. 
The colloidal form of matter may be looked upon as 



CRYSTALLOIDS AND COLLOIDS. 459 

the probable primary source of the force appearing in 
the phenomena of vitality. 

944. Separation of Colloid and Crystalloid 
Substances. — The unequal diffusion and transfusibility 
of colloid and crystalloid substances affords the ready 
method of separating them from each other. An in- 
strument called a dializer is employed for this purpose, 
consisting of a hoop of gutta percha, or other firm 
material, over which is stretched a diaphragm of ani- 
mal membrane, a film of gelatinous starch, hydrated 
gelatin, albumen, or, what is better than anything else, 
paper metamorphosed by sulphuric acid, known as 
vegetable parchment, (§ 959). The dializer when thus 
constructed looks like a small sieve. Place in the dia- 
lizer a mixed solution of gum and sugar to the depth 
of half an inch and float the instrument upon a con- 
siderable quantity of water in a basin. In twenty-four 
hours three-fourths of the sugar will pass through the 
septum into the water, so free from gum as to be scarcely 
affected by subacetate of lead, and to crystallize on 
evaporation of the external water by the heat of a 
water-bath. Many interesting applications of this prin- 
ciple are made in chemical analysis, especially where 
organic substances are concerned. Defibrinated blood, 
milk and other organic fluids mixed with arsenious acid 
are retained in the dializer while the greater part of the 
arsenious acid passes out into the water almost entirely 
free from organic matter. This principle enables us to 
understand why animal and vegetable juices are re- 

944. How may colloid and crystalloid substances be separated ? 



460 ORGANIC CHEMISTRY. 

tained in their own proper tissues while nutrient fluids 
are absorbed and pass into the circulation. 

945. Explanation. — In all these cases the septum of 
the dializer is a colloid substance softened with water 
so united with it as to form a hydrate. The crystalloid 
substance readily diffuses into the combined water of 
the colloid septum, and is taken away by the free water 
on the other side ; but the colloid substance in the dia- 
lizer has but a very feeble power of uniting with the 
combined water of the septum, and hence it is almost 
wholly retained in the dializer. 

Note. — We are indebted to Prof. Graham (Chemical News, London, 1861,) 
for this view of the comparative properties of crystalloid and colloid sub- 
stances. 



CHAPTER II. 

VEGETABLE CHEMISTRY. 

946. Germination. — Before the processes of trans- 
formation of the materials of the earth and atmosphere 
into the innumerable products of the vegetable world 
can commence, a rudimental plant must be developed 
from the seed. The seed itself contains the materials 
for its production. These are principally starch, and 

945. How are these phenomena explained? 946, What is said of ger- 
mination and the changes which attend it ? 



VEGETABLE CHEMISTRY. 461 

gluten,* or the other substances analogous to each, which 

are hereafter described. The first stage in the process is 

the absorption of moisture and oxygen from the air, and 

the consequent production of diastase.^ 274 

This substance has the remarkable prop 

erty of converting starch into sugar, and 

rendering soluble all of the remaining 

gluten of the seed. By the appropriation 

of these materials, which have been stored 

up for it in the seed, the germ is developed 

into a perfect plant. It lets down its 

roots into the soil in search of mineral 

food, and lifts its leaves into the atmosphere, from which 

it is to derive its principal nourishment. At this point 

the true vegetative process commences. 

947. The Lowest Form of Organization is a 
Cell. — Just how the plant transforms inert inorganic 
substances into organized and living structures we shall 
probably never know. Examinations and inquiries 
have established the fact that the lowest primary form 
of organization we can detect is a cell, a little spherical 
or oval sac consisting of an external membrane enclos- 
ing fluid, gelatinous or semisolid contents. When many 
cells are collected together pressure or other causes 




* Gluten is the stringy substance -which remains on removing the starch from 
dough by long continued kneading. It is further described in a subsequent para- 
graph. 

t Diastase is an oxidized gluten -which is always produced from gluten in germi- 
nation. 



947. Describe the vegetable ceU. 



462 



ORGANIC CHEMISTRY". 



change the primary form so that they assume angular 
cylindrical or fusiform outlines corresponding with the 





277 




positions they occupy or the functions they are to per- 
form. The embryo of the seed from which the plant is 
developed in germination had in its earliest stages the 
form of a single cell, Figure 278. From such a simple 
cell, increasing by enlargement and subdivision, the 
whole embryo as seen in the seed before germination is 
produced. The single enlarged cell divides by the for- 
mation of a cross partition into ' two cells, Figure 279, 
one of them into two more, Figure 280, and the^pro- 
cess being continued by the formation of partitions in 
two directions, Figure 281, a collection of cells is formed 
all essentially like the first. By a continuation of this 



378 



279 



'"•■".■ii^ 



280 




process the embryo is completed as it is seen in the 
seed. The stem, root, and leaves of the plant or tree 



VEGETABLE NUTRITION. 463 

are made up by the accumulation of a multitude of 
cells. 

948. Vegetable Nutrition. — Every leaf is a net to 
catch, the fertilizing constituents of the air and appro- 
priate them to the uses of the plant. It drinks them 
in through its countless pores, while the root supplies 
the remaining material and sends it upward in the 
rising sap. All of these materials meet in the leaf, 
which is the laboratory in which their conversion into 
vegetable matter is to be accomplished. The light and 
heat of the sun co-operate with the vital forces of the 
plant in the transformation which succeeds. 

949. Whatever proportion of carbonic acid and water 
may be employed as the raw material, it is obvious, by 
comparison of their composition with that of vegetable 
substances, as hereafter given, that the oxygen is fur- 
nished in larger quantity than is required. Water alone 
yields a sufficient supply of this element, and more than 
enough for most substances that are to be formed. As 
the process of transformation proceeds, this gas is there- 
fore constantly thrown off into the air. It is the refuse 
of the manufacture. Inasmuch as the evolution takes 
place from the leaf and other green parts of the plant, 
it is reasonable to suppose that this is the point where 
the process of transformation is principally conducted. 
The gum, sugar, or other materials produced, are dis- 
solved in the descending sap, and transformed into 
other products, in the course of their circulation. 

948. What is the office of leaves of plants ? 949. What gas is evolved 
from plants ? 




464 ORGANIC CHEMISTRY. 

950. The agency of the leaves of plants in absorbing 
and decomposing carbonic acid, may be illustrated by 

the simple means represented in the 
figure. A glass funnel being filled with 
leaves and slightly carbonated water, 
is exposed to the sun. Oxygen gas 
is gradually evolved from the absorp- 
tion and decomposition of the carbonic 
acid, and collects in the tube of the funnel. The oxy- 
gen may be tested by the usual means. The inversion 
of the funnel without loss of its contents, is easily 
effected, by covering it with a saucer and turning it in 
a pail of water. 

951. For certain transformations of material in plants, 
the evidence is entirely conclusive. The sugar beet and 
turnip are sweetest in the earlier stages of their growth. 
Later in the year they become hard and fibrous. This 
change is undoubtedly owing to the conversion of the 
sugar contained in the sap into woody fiber. In the 
ripening of grain, the sweet and milky juice of the 
young plant is converted into starch. Both hay and 
grain which are harvested too late, are deteriorated by 
the conversion of a portion of their starch and sugar 
into wood. In the ripening of fruits a portion of their 
acid is converted into sugar, as is evident from their 
change of flavor. 

952. Office of the Root. — The agency of the roots 



950. How may the evolution of oxygen by leaves be proved by experi- 
ment ? 951. What transformations occur in plants ? 952. How is the 
action of the roots illustrated by experiment ? 




MOTION OF FLUIDS IK PLANTS 465 

in supplying the plant with its mineral food, may be 

illustrated by the apparatus represented in the figure. 

In preparation for the experiment, a glass 283 

funnel is tightly covered with a piece of 

bladder, and then filled with a solution 

of sugar or salt. A tube is then fitted, 

air tight, to its extremity. A glass vial, 

from which the bottom has been removed, 

may be substituted for the funnel in this 

experiment. On placing the apparatus, 

thus arranged, in a vessel of water, the 

latter penetrates the animal membrane, 

knd adds itself to the contents of the fun 

nel. The flow of the water is called endosmose, and is 

made appreciable to the eye by the rise of liquid in the 

tube. An exosmose, or flow of a small portion of the 

contents of the funnel outward, takes place at the same 

time. 

953. Motion of Fluids in Plants. — The delicate 
cells of which the extremities of rootlets are composed, 
are filled with water holding in solution gum, sugar, 
and other organic compounds, most of which are in the 
colloid state. Hence the soluble salts contained in the 
hygroscopic water adhering to the rootlets or adjacent 
soil pass inwards almost as freely as into pure water, 
and pass in the same manner from cell to cell until they 
are transformed into the colloid substances required to 
build up the tissues of the plant. It is a mistake to 

953. How is this principle applied to explain the motion of fluids in 
plants ? 



466 OEGANIC CHEMISTRY. 

suppose the rootlets of common plants to be flooded 
with water. In such a condition of the soil most plants 
would die. In a soil adapted for the healthy growth 
of plants the particles of soil and the roots of plants 
are merely moistened with hygroscopic water, which 
affords soluble salts to the roots but is not adapted to 
carry away the juices of the plant if they could flow 
outward. Hence the illustration given above is appli- 
cable to the action in the roots of plants only so far as 
to explain the inward flow, endosmose, of materials to 
nourish the plant. The action above described occurs, 
more or less, in all the organs of plants through the 
walls of the minute cells of which they are composed. 
The transpiration of water from the leaves induces a 
flow of the sap upwards and the constant organization 
of materials by the growth of all parts of the plant 
creates a tendency for the nutrient material to pass to 
all parts of the plant where it is wanted. The relation 
of the plant and soil is further considered in a sub- 
sequent chapter. 

954. Constituents of Plants. — Among the more 
important of vegetable substances, are wood, starch, 
sugar and gluten. "Woody fiber forms the mass of the 
plant ; starch and gluten collect in the seed ; while 
sugar and gum exist principally in the sap and fruit, or 
exude from the bark. 

954. Mention some of the more important vegetable substances. 



wood. 46^ 



Wood. 



955. "Woody Fiber. — The term cellulose or cellulin is 
applied to the substance of woody fiber. It is composed 
of C 12 H 10 O 10 , or C 24 H 20 O 20 . The varieties of woody mat- 
ter differ in color, texture and induration ; but when freed 
from various foreign matters, they leave a white translu- 
cent residue. Certain piths, linen, cotton, filtering paper, 
and some other allied substances, are nearly pure cellu- 
lose. It is composed of carbon, hydrogen and oxygen. 
Its molecule contains twelve atoms of carbon, to ten of 
hydrogen and ten of oxygen. It constitutes the solid 
mass of all vegetable organs, whether hard and firm, 
like the fiber of the oak ; soft, like the pulp of fruits ; 
or fibrous, like cotton and flax. In one or the other of 
its varieties it thus serves us for shelter, clothing and 
food. It forms in plants the cells in which the vege- 
table juices are contained, and the veins or pores 
through which they circulate ; and has thence received 
its name of celhdose. In wood, these cells are often 
lined or filled with a substance of nearly similar com- 
position, to which the name of lignin has been given. 
Other matters passing through the plant are gradually 
deposited with cellulose in the older cells, so that an 
analysis of old cells gives results slightly different from 
young cells from which the formula for cellulose is 
obtained. 

956. Action of Be-agents. — Cellulose is insoluble 

955. Mention different forms of woody fiber— and its composition. 
056. What is said of the action of re-agents upon woody fiber ? 



468 ORGANIC CHEMISTRY. 

in water, alcohol, ether and oils. It is acted upon by 
acids and alkalies, the action differing according to the 
degree of concentration of the re-agent. A large num- 
ber of interesting compounds are thus produced, some 
of which are to be described. Yegetable cellular tis- 
sue, in its succulent form, is easily digestible, but when 
it has become incrusted by true woody matter, it is no 
longer digestible, or in a condition to serve as nutri- 
ment to the higher orders of animals. 

957. Effect of Sulphuric Acid on Wood. — Sul- 
phuric acid chars or blackens wood by abstracting a 
portion of the oxygen and hydrogen which it contains. 
The carbon is then left in excess, with its characteristic 
color. This action of sulphuric acid is a consequence 
of its strong affinity for water, the elements of which 
it appropriates from most organic substances. When 
pure cellulose is acted on by the cold acid a magma is 
formed which becomes blue on the addition of free 
iodine. If it is much diluted and boiled it is converted 
first into dextrin and subsequently into glucose. Linen 
rags may be made to furnish more than their own weight 
of this latter substance. 

958. Wood converted into Sugar. — Wood may be 
converted into sugar, by causing it to combine, chemi- 
cally, with four additional molecules of water. This 
addition gives it the precise composition and properties 
of grape sugar, and, in fact, converts it into that sub- 
stance. Poplar wood is found best suited for the pur- 

957. What is the effect of sulphuric acid on wood ? 958. How may 
wood be converted into sugar ? 



VEGETABLE PAKCHMEKT. 469 

pose, and can be made to yield four-fifths its weight. 
To effect the conversion, the wood is first reduced to 
saw-dust, then moistened with somewhat more than 
its own weight of oil of vitriol, and left to stand for 
twelve hours. Being subsequently pounded in a mor- 
tar, the nearly dry material becomes liquid. It is then 
boiled with addition of water, and the transformation 
is completed. It only remains to remove the sulphuric 
acid, and evaporate the syrup. The former object is 
effected by the addition of chalk and subsequent filtra- 
tion, and the latter, as usual, by boiling. 

959. Vegetable Parchment. — By the action of sul- 
phuric acid upon paper, a useful material known as 
vegetable parchment is obtained. It is prepared by 
plunging unsized paper for a few moments at a temper- 
ature of 60° into a mixture of oil of vitriol with half 
its bulk of water. The proportions are important ; if 
the acid is weaker, the fiber is converted into gum, if 
stronger it is corroded. The paper must be quickly 
withdrawn and washed, first with water, then with a 
weak solution of ammonia, and lastly with water again. 
In this process the outer surface of the fibers appear to 
have become converted into a glutinous substance by 
which the fibers are cemented together, and the pores 
filled up. It is now tough, translucent, nearly imper- 
meable to water, takes ink well, forming a useful sub- 
stitute for ordinary parchment. It is put to some im- 
portant uses in the arts. It may be substituted for 

959. How is vegetable parchment prepared 9 



470 ORGANIC CHEMISTRY. 

bladder as a septum in electrolytic operations with 
great advantage. 

960. Effect of Nitric Acid. — Nitric acid gradually 
consumes wood and other organic matter, as effectually 
as if they were burned by fire. The final products of its 
action are also the same as those of ordinary combus- 
tion. This action is accompanied with the evolution 
of orange fumes, as when the same acid acts on metals. 
The first effect of nitric acid is to stain wood yellow ; 
for which purpose it is sometimes employed. By vary- 
ing the strength and temperature of the acid a variety 
of compounds are obtained. 

961. Pyroxylin or Gun Cotton. — This remarkable 
substance is prepared by dipping clean carded cotton 
into a mixture of equal measures of oil of vitriol and 
nitric acid. Small portions of the cotton are immersed 
completely in the cooled mixture of the acids, permit- 
ted to remain ten or twenty minutes, then withdrawn, 
the excess of acid pressed out and plunged into a large 
volume of cold water. The cotton is w r ashed until the 
last trace of acid disappears, and cautiously dried at a 
temperature not exceeding 212°. During this opera- 
tion scarcely a change of form occurs, but a remarka- 
ble chemical alteration takes place, and the fiber ac- 
quires entirely new properties. A certain number 
of atoms of hydrogen are abstracted and an equal 
number of equivalents of peroxide of nitrogen (N0 4 ) 
supply their place. It is more harsh and brittle than 

960. What is the effect of nitric acid on wood ? 961. How is gun- 
cotton prepared ? 



PYROXYLIN. 471 

before, and highly electric. It has gained weight and 
is remarkably combustible. Clean paper, tow, linen, 
sawdust, and other forms of cellulose yield similar com- 
pounds. 

962. Use of Pyroxylin. — Pyroxylin is not likely, 
for several reasons, to supersede gunpowder for use 
in fire-arms. It takes fire at about 400°, which is 
about 200° below the temperature required for the 
ignition of gunpowder, and is much more liable to pro- 
duce accidental explosions. In the open air, when in- 
flamed it flashes off without smoke, smell or residue ; 
within the gun-barrel the extreme suddeness of its ex- 
plosion produces great strain, and is apt to burst the 
barrel. Its explosive force depends, like that of gun- 
powder, on a sudden combustion throughout its whole 
substance, and consequent evolution of a large volume 
of mixed gases and vapor. Of these, carbonic acid, 
nitrogen and aqueous vapor are the principal. In cer- 
tain cases it may be used to advantage. In mining 
operations it may be driven into borings above the head 
of the miner, and on explosion produces less fume. In 
addition it has the advantage of leaving no train by 
leakage from the vessels in which it is stored. It 
may be exposed to damp air and even to prolonged im- 
mersion in water without injury if subsequently dried. 
"Weight for weight its explosive force is three or four 
times that of the best musket powder. Pyroxylic paper 
is remarkable for the intensity of its electricity when 
slightly rubbed. 

962. What are the uses of pyroxylin ? 



472 ORGANIC CHEMISTRY. 

963. Collodion. — The solution of pyroxylin in a 
mixture of alcohol and ether, is known under the name 
of collodion. When this solution is exposed to the air 
for a few moments in the form of a thin layer, the sol- 
vent evaporates, leaving the pyroxylin in a transparent 
film. Spread over excoriated surfaces an artificial cuti- 
cle is produced by which they are protected from the 
action of the air. For medical purposes the properly 
prepared cotton is dissolved in a mixture of ninety 
parts of ether and ten parts of alcohol. Collodion has 
its most extensive application in the art of photogra- 
phy. Impregnated with the sensitive salt, which is 
acted upon by light and diffused over a glass plate, it 
forms a surface admirably fitted for the reception of 
photographic impressions. Photographic collodion re- 
quires for its successful preparation attention to numer- 
ous minute precautions which cannot be given in detail 
here. 

984. Effect of Alkalies on Cellulose. — Weak 
alkaline liquids have but slight action on cellulose, but 
concentrated solutions of the alkalies hasten the decom- 
position of organic substances generally when in con- 
tact with them. Advantage is taken of this action of 
the caustic alkalies for the production of materials de- 
manded in the arts, particularly in the formation of 
oxalic acid. Oxalic acid is an organic acid, found in 
the juices of plants, but which may be obtained also by 
artificial means. One of the cheapest and most pro- 

903. What is collodion ? For what is it used ? 964. What effect do 
alkalies produce upon cellulose ? 



DECAY OF WOODY FIBER. 473 

ductive processes consists in treating sawdust with a 
mingled solution of caustic potassa and caustic soda. 
The mixture is carefully heated at the proper tempera- 
ture for some hours, in cast iron pans, and the result is 
a residue containing a large quantity of the mixed oxa- 
lates of potassa and soda. From these salts the oxalic 
acid may be separated and obtained in large crystals. 
Sawdust by this treatment yields half its weight of 
oxalic acid. 

965. Action of other Re-agents. — A solution of 
chlorine acts but very slowly upon cellulose. Concen- 
trated hydrochloric acid dissolves cellulose and deposits 
it on immediate dilution with water. A solution of 
oxide of copper in ammonia dissolves it in most of its 
forms, and deposits it, unaltered in composition,- on 
acidulation with an acid. 

966. Decay of "Woody Fiber. — "Wood in a moist 
state exposed to the air gradually undergoes decomposi- 
tion. The rapidity of the destructive process depends 
much upon the texture of the wood, and the quantity 
and quality of the foreign matters associated with it ; 
some promoting and others retarding decay. Decom- 
position goes forward most rapidly in the young spongy 
sap wood, since this admits the air more freely, and 
contains a proportionally larger amount of albuminous 
substances than the older portions. A species of fer- 
mentation is occasioned by the nitrogenized constitu- 
ents ; oxygen is absorbed, carbonic acid and water is 

965. Mention the action of other reagents. S66. W r hat is said of the 
decay of woody fiber? 



474 ORGANIC CHEMISTRY. 

exhaled, and the wood crumbles down into a brownish 
mould called humus ^ ulmin and gein, substances rich 
in carbon, which element has been more slowly con- 
sumed than the other constituents. When there has 
been an abundant supply of moisture, and deficient 
access of air, the mass has a different composition and 
a different aspect ; water has combined with the wood 
and it remains white as seen in stumps and the interior 
of some trees. 

987. Preventives of Decay. — When wood is kept 
dry, or when submerged in water, it is little prone to 
change. In mummy cases, in the piles of bridges, and 
in submerged forests, wood has remained for centuries 
in a good condition. To prevent the action of air and 
moisture and the attacks of vegetables and insects is a 
matter of high importance. The tendency of wood to 
decay may be checked by imbuing it with certain oils, 
tars, oxides and salts. Alum, sulphate and pyrolignate 
of iron, sulphate of copper, corrosive sublimate, and 
chloride of zinc are some of the substances which have 
been thus applied. Wood, sail cloth, cordage, etc., 
have been pretty effectually preserved by steeping them 
for a given time in crude kreasote. By coating wood 
with a layer of resin, tar, or paint impervious to air and 
moisture, preservation is to a great extent accomplished. 
The superficial charring of piles and posts which are to 
be placed in the earth has been resorted to for a long 
time as a means of preservation. Railroad ties have 

967. How may the decay of wood be prevented ? 



WOOD SPIRIT. 475 

been treated in this way. Casks designed to contain 
water for the use of mariners are charred in the interior. 
The most effectual method consists in directing a jet of 
inflammable gas against the structure to be preserved, 
by which the wood is burned to the required depth. 

968. Effect of Heat upon Woody Fiber. — Wood 
heated with free access of air, takes fire, as every one 
knows, and is consumed. The greater portion of the 
mass escapes as carbonic acid and water, while a minute 
quantity of earthy material, ash, is left. If, however, 
the wood is shut off from contact with the air and sub- 
mitted to destructive distillation, a variety of products 
is the result. There is a re-arrangement of the atoms 
of the wood itself without the help of oxygen or other 
elements. Some of the most interesting of these com- 
pounds are noticed below. 

969. Wood Spirit. (C 2 H 4 2 ). — In destructive dis- 
tillation the products are gases, liquids, and a solid, 
carbon or charcoal. The wood is heated in iron retorts, 
connected with a proper condensing apparatus, and the 
inflammable gaseous products conducted into the fur- 
nace so as to serve as fuel. The liquid which is con- 
densed contains a variety of substances, water forming 
a large part ; among these is wood spirit or amylic alco- 
hol. This when separated is in many respects like the 
common vinous alcohol, being a limpid, colorless, in- 
flammable liquid, of a penetrating spirituous odor, and 
a disagreeable burning taste. It may for most purposes 

968. What is the effect of heat upon woody fiber? 969. What is wood 
spirit ? 



476 ORGANIC CHEMISTRY. 

replace common alcohol, and having great solvent 
power is of considerable value in the arts. 

970. Wood Vinegar. (HO,C 4 H 3 Q 3 ).— Wood vine- 
gar, or pyroligneous acid, has the same composition as 
acetic acid obtained from oxidation of dilute alcohol. It 
is largely used in dyeing, in the form in which it ap- 
pears in market ; it is colored dark by tarry matters, 
and has a smoky smell. When separated from impuri- 
ties it is a clear, colorless liquid, having a sharp pleas- 
ant acid taste. 

971. Kreasote. — Kreasote appears to be the princi- 
pal source of the peculiar odor and preservative quali- 
ties of wood smoke. When pure it is a colorless, 
somewhat oily liquid, of high refractive power, of a 
penetrating smoky odor, and a burning taste. It is 
but slightly soluble in water, not readily inflamed, 
and burns with a smoky flame. It is an irritant poison 
when undiluted, but when largely diluted, it has been 
found effectual in checking vomiting, and as an appli- 
cation in tooth-ache for the destruction of the nerve. 
It is the most powerful antiseptic known. A solution 
of it containing not more than one part in a hundred, 
preserves meat from putrefaction. The preservative 
effect of smoke, as well as of crude pyroligneous acid, 
is owing to the presence of a small amount of this sub- 
stance. Kreasote consists of carbon, hydrogen and 
oxygen, but its exact composition is yet uncertain. 
The formula C ]G IIio0 2 has been assigned to it. 

970. What is wood vinegar ? 971. For what is kreasote used ? 



WOOD TAB. 477 

972. "Wood Tar. — Wood tar is a mixture of various 
oils and volatile crystalline solids composed principally 
of carbon and hydrogen. There are several varieties 
of tar. The kind so largely employed in the arts, as in 
ship-building, is obtained by subjecting to a rude pro- 
cess of distillation the roots and wood of the resinous 
pine ; another variety of tar results from the destruct- 
ive distillation of hard wood. Coal tar is a product 
resulting from the destructive distillation of coal. Wood 
tar is insoluble in water but soluble in alcohol, and is 
extremely rich in carbon, which gives it in part its black 
color. Tar from pine wood, when distilled, yields prin- 
cipally impure oil of turpentine, leaving a black resi- 
nous mass which constitutes ordinary jpi tch. Tar from 
hard wood, when distilled, gives a large number of 
interesting products. One of those, kreasote, has al- 
ready been described, others are to be noticed. 

973. Compounds obtained from Wood Tar. — Eu- 
pion is a very light oil of a peculiar greasy character, 
very inflammable and burns with a bright flame. The 
formula C 5 H 6 has been assigned to it. 

Kapnomor is a colorless oil of high boiling point 
and rather lighter than water. It has an odor of gin- 
ger, and a taste at first feeble, but afterwards becoming 
connected with an insupportable sense of suffocation. 
Its composition is thought to be C 20 HnO 2 . 

Picamar is a viscid, colorless, oily liquid, of greater 



972. What substances are contained in wood tar ? 973. What valuable 
compounds are obtained from wood tar ? 



478 ORGANIC CHEMISTRY. 

density than water, haying a feeble odor but intensely 
bitter taste. 

Pittacai is a solid compound of deep bine color. 

Cedriret is also a solid and may be readily crystal- 
lized. 

974. Paraffin. — Paraffin is perhaps the most inter- 
esting substance found among the solid constituents 
of hard wood tar. It likewise occurs among the pro- 
ducts of distillation of peat, and in several mineral 
tars and some kinds of petroleum. At ordinary tem- 
peratures paraffin is a hard white crystalline solid, 
without taste or odor, and resembling spermaceti both 
to the touch and appearance. It melts at about 111°, 
and may be distilled over at a higher heat unchanged. 
Paraffin is insoluble in water. It burns with a bright 
smokeless flame ; candles made of it burn like those 
made from the finest wax. It resists the action of acids, 
alkalies, chlorine and potassium, and it is called paraffin 
(from parum affinis) on account of its inertness or 
want of affinity. It is composed wholly of carbon and 
hydrogen. 

975. Substances resulting from natural Changes 
of "Woody Fiber. — Peat. The vegetable origin of 
this substance is at once evident on inspection. It is 
mainly the product of the slow decay of certain species 
of marsh plants under water. Peat bogs were in the 
first instance marshes, which have become filled up by 
the annual growth and decay of surface vegetation. The 

974. What is the appearance and use of paraffin ? 975. What other 
substances are produced from woody fiber. 



coal. 479 

process of accumulation is comparatively rapid. The 
different layers vary greatly, those near the surface 
consisting of the partially decayed stems of mosses and 
roots, while the deeper layers exhibit little or no traces 
of vegetable structure, and in some instances are found 
converted into a true bituminous coal. In some coun- 
tries it is extensively used as fuel. By distillation it 
yields many valuable products. 

976. Coal akd other Combustible Minerals. — 
Coal and many of its allied products are obviously of 
vegetable origin; but the circumstances under which 
they have formed and deposited in their present locali- 
ties, are not well understood. 

Lignite generally retains its woody structure to a 
considerable extent. It has a brown color, and some- 
times resembles indurated peat. When heated it ex- 
hales a bituminous odor and burns with a bright flame. 

The formation of bituminous coal is a consequence 
of the decay of vast accumulations of vegetable matter 
which has been buried in the earth during previous 
ages of its existence. Of this there are many varieties, 
Cannel, Newcastle and Breckenridge being among the 
most valuable. Bituminous coal burns with a bright 
luminous flame, and has a high value as a fuel and a 
source of illuminating gas. Where bituminous coal 
has been subjected to great heat, more carbon and hy- 
drogen are expelled, and anthracite coal remains. A 
similar change takes place when bituminous coal is 

976. What is said of coal, lignite, bituminous coal and coke ? 



480 ORGANIC CHEMISTRY. 

heated by artificial means, the resulting solid mass tak- 
ing the name of coke. 

977. Transition from "Woody Tissue to Anthra- 
cite Coal. — There is no sharp line of demarkation be- 
tween woody tissue and the hardest anthracite. From 
the highest to the lowest layer in the peat bog there is 
a gradual transition, the upper being made up of slightly 
changed vegetable fiber, the lower passing sometimes 
into true bituminous coal. Specimens of bituminous 
coal may be found which have less and less volatile 
matter, approaching gradually the character of anthra- 
cite. If comparison be made of the composition of 
these different substances, starting with woody tissue, 
which consists of carbon, hydrogen and oxygen, it will 
be seen that the proportion of oxygen diminishes 
rapidly, and that of hydrogen more slowly as it passes 
towards anthracite, in which form it consists of nearly 
pure carbon. Besides the carbon however, there are 
small quantities of oxygen, hydrogen, nitrogen, sulphur, 
and various mineral matters, constituting the incom- 
bustible residue or ash which is chiefly silicious matter 
with carbonate of lime and oxide of iron. 

978. Bitumen, Asphaltum. — Asphaltum, or mineral 
pitch, occurs on the shores of the Dead Sea, in Barba- 
does and Trinadad, and in several other localities. In 
many instances it is the product of the action of an 
elevated temperature upon vegetable bodies. Pure 
asphaltum is black or dark brown, has a slight bitumi- 

977. What is said of the transition from woody fiber to anthracite 
coal? 978. Where is bitumen obtained? How is it used? 



MINERAL OILS. 481 

nous odor, a resinous fracture ; it softens when heated 
and burns with a smoky flame. Sometimes bitumen 
forms irregular deposits which impregnate the strata 
around ; sometimes it occurs in regular beds similar to 
the deposits of true coal. Bitumen, of various degrees 
of purity and from various sources, is used in combi- 
nation with chalk, sand, lime, etc., as a material for 
pavements and cements. The finer kinds of asphaltum 
are employed in the formation of a species of black 
varnish or enamel for leather. 

979. Mineral Oils. — Inflammable oily bodies, issuing 
often in large quantities from fissures in connection 
with coal strata, and in other localities, have been 
known from early historical time. There is reason to 
suppose that they owe their origin to the action of in- 
ternal heat upon beds of bituminous rock strata. These 
are called naphtha or petroleum, according to their 
character. The term naphtha is given to the thinner 
and purer varieties of rock oil, the darker and more 
viscid liquids bear the name of petroleum. 

980. Naphtha. — The finest specimens of naphtha 
are obtained at Amiano, in Northern Italy. It occurs 
also at other places in Italy, in the regions bordering 
the northwest side of the Caspian Sea and in various 
other localities. When pure, it is a light, colorless, in- 
flammable and very volatile liquid. It has great sol- 
vent powers, dissolving readily caoutchouc, camphor, 
fatty and resinous bodies generally ; and when hot, also 

979. What is said of mineral oils? 980. What is naphtha? How 
used? 



482 ORGANIC CHEMISTRY. 

sulphur and phosphorus. The entire absence of oxy- 
gen from its composition, adapts it perfectly to the pres- 
ervation of the metals potassium and sodium in their 
metallic condition. 

981. Petroleum. This term, as stated, is applied to 
the darker and more viscid rock oils. The oil varies 
considerably color and in thickness, some being very 
fluid and comparatively light in color, others quite 
viscid and nearly black. Its specific gravity is from 
0.83 to 0.89. The Burmese petroleum has long been 
celebrated. The discovery of immense quantities of 
petroleum in Pennsylvania and other parts of the Uni- 
ted States, and in Canada, is of vast economic impor- 
tance. This occurring just as the ordinary sources of 
artificial illumination were diminishing, or were cut off, 
heightened the value of the discovery. 

982. Composition, Purification and Use. — The oil 
consists of carbon and hydrogen, and is a mixture of 
several oils having different densities and different de- 
grees of volatility. The purification is effected chiefly 
by distillation and alternate washings with an acid and 
an alkali. By these different processes the greater 
part of the color and offensive odor is removed, and 
the lightest and heaviest oils are separated from those 
of medium density. These medium oils are those that 
may be properly used in ordinary illumination. The 
lighter are too volatile for common lamps, forming as 
they do with the air a dangerous explosive compound. 
They replace to a great extent turpentine in the prep- 

981. Where is petroleum obtained ? 982. How is petroleum purified ? 



COAL OILS. 483 

aration of varnishes and in painting. The heavier oils 
are of value as lubricators. 

983. Distillation of Coal. — "When the distillation 
of bituminous coal is effected in vessels from which the 
air is excluded, there result many products. A large 
amount of volatile matter is expelled partly in the form 
of uncondensible gases, and partly in the form of va- 
pors, which, when reduced to the ordinary temperature 
of the air, constitute liquids or solids, whilst a large 
proportion of the materials remains behind in the form 
of coke. Among the gaseous products, the most im- 
portant are marsh gas, olefiant gas, hydrogen, carbonic 
acid, carbonic oxide, sulphuretted hydrogen and ammo- 
nia. These gaseous products, after purification, may 
be used as illuminating gas. The liquid portions con- 
tain water and various hydrocarbons which form coal 
naphtha, besides a quantity of viscous matter known 
as coal tar. 

984. Coal Oils. — If the heat of the distillation be 
less than that applied in the manufacture of illuminat- 
ing gas, a smaller quantity of permanent gaseous mat- 
ter is formed, and a proportionally larger amount of con- 
densible oils. By the distillation of rich bituminous 
coals at a comparatively low temperature, the illumi- 
nating coal oils at first sold as kerosene are produced. 
They are hydrocarbons, and in most respects correspond 
to the natural oils described in the section on petro- 
leum. 

983. What is said of the distillation of coal ? 984. What is coal oil ? 



484 ORGANIC CHEMISTRY, 

985. Coal Tar and its Derivations. — Coal tar as 
produced in the gas factories, is a very complex sub- 
tance ; it is always alkaline from tlie presence of am- 
monia ; it contains aniline and numerous other bases, 
as well as plienic and acetic acids. "When distilled fetid 
ammoniacal compounds pass over and a light oil, coal 
naphtha^ succeeded by small portions of a heavier oil 
containing a little paraffin. In the latter stages of the 
operation naphthalin is abundant in the distillate, and 
the oil becomes semi-solid as it cools. The black resi- 
due in the retort solidifies on cooling and forms a kind 
of pitch or asphaltum, which is used in the preparation 
of a coarse black varnish. The coal naphtha, like the 
natural naphtha, is found to be a complex substance giv- 
ing by careful distillation the following products — 1, an 
oil of alliaceous odor ; 2, benzole (C 12 H 6 ) ; 3, toluole 
C 14 H 8 ) ; 4, cumole (Ci 8 Hi 2 ) and cymole (C 20 Hi 4 ). The 
naphtha is therefore a mixture of several definite hy- 
drocarbons, among which benzole is the most impor- 
tant. 

986. Benzole. (Ci 2 H 6 ). — This is a very limpid, color- 
less liquid, of a peculiar and rather agreeable odor. If 
exposed to a cold of 32° it solidifies in transparent crys- 
tals, grouped like fern leaves, or in masses resembling 
camphor, which melt at 40°. It is an excellent solvent 
of caoutchouc and gutta-percha, and on evaporation 
leaves them with their peculiar physical character un- 
altered. Benzole dissolves wax, camphor, and fatty 

985. Describe coal tar and its derivatives. 986. What is benzole ? 



ANILINE. 485 

bodies with facility. Its solvent power for fats and oils 
enables it to be used with advantage for removing grease 
stains from articles of silk and woolen, and it is sold for 
this purpose under the name of ~benzine. 

987. Nitrobenzole. (C 12 H b Is"0 4 ). If benzole is 
added, in small portions at a time, to warm fuming ni- 
tric acid, it is dissolved, and on cooling is separated in 
the form of a yellow oil, which, is termed nitro tenzole. 
This oil has a very sweet taste and an odor so nearly 
resembling bitter almonds, that it has nearly superseded 
the latter in the preparation of perfumery and the 
scenting of soaps. By adding to nitro benzole a mix- 
ture of equal parts of alcohol and hydrochloric acid, 
and introducing a few fragments of zinc, a volatile arti- 
ficial base of much interest, aniline, is produced. 

988. Aniline. (C 12 H 7 1s"). — This base is a limpid liquid 
of an agreeable vinous odor, and an aromatic burning 
taste ; is very acrid and poisonous. It combines with 
acids forming salts, most of which crystallize readily. 
Aniline may be prepared from various sources and by 
a variety of reactions, but is chiefly obtained by action 
of reagents on substances procured from coal tar. It 
has its chief commercial interest from the fact that it 
is the source of many of the magnificent colors which 
have recently appeared. By the action of various 
oxides and salts upon aniline, a variety of colors are pro- 
duced. A piece of wood dipped in a solution of any 
of its salts gradually acquires an intense yellow color. 

987. How is nitro-benzole obtained ? 988. What is aniline? 



486 ORGANIC CHEMISTRY. 

The beautiful purple known as mauve, and the rich 
crimson termed magenta, are aniline products. A 
splendid blue and a variety of other tints have their 
source in aniline. 

989. Naphthalhst. (C 20 H 8 ). — This substance comes 
over late in the distillation of coal tar. It is a solid at 
ordinary temperatures, which when pure forms large 
colorless crystalline plates. It has a faint, peculiar 
odor, is unctuous to the touch and evaporates slowly at 
the common temperature of the air. From it many 
interesting chemical compounds have been prepared. 

990. Phenic Acid. (HO,C 12 H 5 0). This substance, 
also termed carbolic acid, is one of the constituents of 
coal tar. "When pure, phenic acid forms long colorless 
crystals, which melt at 95°, and in the presence of a 
minute trace of moisture go into solution. When in 
solution it greatly resembles kreasote, in many particu- 
lars, having the smoky odor, burning taste and antiseptic 
properties of this body ; indeed, much of the commercial 
kreasote consists of phenic or carbolic acid. It is valu- 
able as a disinfectant. 

991. Picric Acid. (HO,C 12 H 2 (NO ) 3 0).— Picric acid, 
often called carbazotic acid, is a solid crystalline 
body of an intensely bitter taste. It is prepared by 
the action of nitric acid on a number of substances, 
among which are aniline and the oil of tar. It and its 
salts are used for coloring, giving to silk a beautiful 
yellow color. Its coloring power is so great, that the 

989. Describe napthalin. 990. What is phenic acid? 991. What is 
picric acid? 



STARCH. 487 

aqueous solution may be diluted with several hundred 
times its bulk of water without losing its yellow color. 
But a small portion of the different compounds 
obtained directly or indirectly from coal tar — a sub- 
stance not long since regarded as worthless — have been 
here described. The source of these was originally in 
the form of vegetable tissue. 

Starch. 

992. Starch. (C 12 H 10 O 10 ). — This, the lowest form 
of organized vegetable material, is found widely dis- 
tributed in the vegetable kingdom, being almost uni- 
versally present in plants of higher organization, accu- 
mulating abundantly in the cellular tissue of certain 
parts of the organism. As usually seen, it is in the 
form of a white glistening powder, or in columnar 
masses, which, when pressed between the fingers, emit 
a peculiar sound, and produce a feeling of elasticity. 
Under the microscope it is seen to consist of small 
grains, usually rounded or spheroidal, rarely angular, 
differing in size and shape according to the character 
and age of the plant from which it is extracted. It is 
mostly in the form of starch that the plant stores up 
elaborated material which is to be used either in its own 
future growth, or in the propagation of its kind. Man 
uses this stored material for food, which he finds most 
abundantly in grains and other seeds, in the tubers of 

992. Where is starch obtained ? 



488 ORGANIC CHEMISTRY. 

the potato plant, in many fruits, and in the pith of cer- 
tain trees. 

993. Starch Grains. — The grains of starch have a 
size varying from about ^o °f an inch to less than 
__?__ of an inch in diameter. Under the microscope, 
they generally exhibit a series of concentric rings, which 
are supposed to have been formed by a deposition of 
successive layers of starchy matter within an external 
envelop, and a point, hilum, may generally be observed 
upon some part of the grains, which has been regarded 
as the spot where they adhered to the cell containing 
them. Examined by polarized light, potato starch, and 
some other kinds, present the appearance of a black cross, 
the centre of which corresponds to the hilum. In wheat 
starch, this cross is not easily observed. By this char- 
acteristic, as well as by the size and shape of the grains, 
mixtures and adulterations of various starches may be 
easily detected by the microscope. 

994. Varieties of Starch. — The starch of commerce 
is usually obtained from potatoes or wheat. A large 
amount of a fine quality, and extensively used for 
cooking, is obtained from maize. Bice also furnishes a 
certain quantity. The grains of rice starch are angu- 
lar. Other varieties are found to some extent in the 
market. Sago is a starch from the pith of the sago 
palm, and which is usually granulated. Tapioca is the 
starch of the jatropha manihot, which is pressed 
through a colander and dried, giving granular, irregu- 

993. What are starch grains ? 994. What are the varieties of starch ? 



STARCH. 



489 



lar masses. Arrow root is the starch of the root of the 
maranta arundinacea, and of one or two other tropical 
plants. 

995. Starch from Potatoes. — Starch is prepared 
from rasped potatoes by washing them on a seive. The 
water becomes milky, 
as it passes through, 
from the fine starch 
grains which it car- 
ries with it. These 
are allowed to settle, 
and being collected 
and dried, are brought 
into commerce as po- 
tato starch. A cot- 
ton-cloth may be sub- 
stituted for the seive 
in this experiment. 

Figure 284 will convey an idea of the appearance of 
the granules of potato starch magnified 400 diameters. 

996. Starch from "Wheat. — If wheat flour is moist- 
ened with water and exposed to the air, it enters into 
a putrefaction which destroys, in the course of a few 
days, the other constituents and leaves the starch unaf- 
fected. The residue being then washed and dried, the 
manufacture is completed. 

997. Properties of Starch. — Starch is insoluble in 
cold water, as its method of preparation would indicate ; 




995. How is starch prepared from potatoes ? 996. How is starch made 
from wheat ? 997. What are the properties of starch ? 




490 ORGANIC CHEMISTRY. 

but is rapidly disintegrated by hot water. When 
heated with water, the granules swell, burst, and allow 
their contents to be mingled with the water, producing 
a nearly transparent glutinous mass, in which form it 
is used for stiffening various fabrics and articles of 
wearing apparel. The swollen appearance which pota- 
toes, rice, and most other vegetables assume when 
boiled is due to a distention of their starch granules 
385 through an absorption of water at the boiling 
temperature. Starch is insoluble in alcohol 
and in ether. Iodine may be used as a test 
for starch, as described under the head of 
iodides. 

998. Conversion of Starch into Sugar. — Starch, 
like woody fiber, may be converted into sugar through 
the agency of sulphuric acid. A dilute acid contain- 
ing only j\ of its volume of oil of vitriol, is brought 
to the boiling point, and the starch then added by 
degrees while the boiling continues. Long boiling is 
required to effect a complete conversion. An infusion 
of brewer's malt has the same effect as the dilute acid. 
The sulphuric acid is then to be removed, and the syrup 
concentrated as before described. The sugar in this 
case also is grape, and not cane sugar. Such sugar is 
manufactured largely in Europe for adulterating cane 
sugar. In England its manufacture is prohibited by 
law. 

999. Conversion or Starch into Gum. — By keep- 

998. How is starch converted into sugar ? 999. How is starch trans- 
formed into gum ? 



Gr U M . 491 

ing the liquid near to the boiling point, without actual 
boiling, the gum called dextrine, is obtained in the above 
process, instead of sugar. It may also be prepared by 
roasting starch, carefully, with constant stirring, until 
it acquires a brownish yellow color. This gum is used 
largely in calico printing, for thickening colors. It is 
also used in making the so-called " fig-paste" and cer- 
tain other kinds of confectionery. The composition of 
starch and gum is precisely the same. 

Gum. 

1000. Gum. (C 12 H 10 O 10 ). — This term is generally ap- 
plied to designate certain vegetable substances which 
possess the same elementary composition as starch; 

Tbhey are not organized like starch, nor are they crystal- 
lizable like sugar ; they either readily dissolve in water 
or swell up into a viscid mass when moistened ; and 
they are tasteless and insoluble in alcohol and in ether. 
Gum is found in the juices of most plants, and in some 
it exists so abundantly that it exudes from the bark of 
the plant, when wounded, as a viscid liquid which sub- 
sequently hardens into globular or tear-like masses. 
Familiar illustration of this may be noticed on peach 
and cherry trees. Gum is an essential constituent of 
the cereals, and of most seeds, and is abundant in many 
vegetables. 

1001. Yaeieties of Gum. — The most important gums 

1000. What is gum ? WTiere found ? 1001. What are the varieties of 
gum? 



492 ORGANIC CHEMISTRY. 

of commerce are gum-arabic, gum-senegal and gum- 
tragacantli. Gum-arabic is the product of a species of 
acacia, which grows abundantly in Africa and Arabia ; 
gum-senegal, the product of a similar tree, has its name 
from Senegal, in Africa, the district from which it was 
originally exported. These gums are freely soluble in 
water; the solution yielded by gum-senegal being 
somewhat thicker than that formed by gum-arabic. 
The pure gummy substance contained in them may be 
precipitated from its solution in water by alcohol, and 
is termed arabin. Gum-tragacanth is the product of a 
shrub found extensively in Asia Minor and Persia, and 
is composed mainly of a substance termed iassorin. 
It swells very much in water and forms a thick adhe- 
sive paste, but can hardly be said to dissolve in it. 

1002. Allied Substances. — Many seeds, such as lin- 
seed, quince seed, and certain roots, such as those of 
the marshmallow, furnish a large quantity of material 
closely resembling gum-tragacanth. The term muci- 
lage is often applied to them. 

1003. Yeqetable Jelly. — This principle, like starch 
and gum, extensively pervades the vegetable kingdom, 
being the body which gives to the juice of many succu- 
lent fruits and roots the property of gelatinizing. In 
composition it is allied to gum. Many algae, fuci, 
and lichens, abound in a gelatinizing principle, and are 
extensively used as food. 

1002. What substances resemble gum? 1003. What is vegetable 
jelly ? 



SUGAR. 493 



Sugar. 



1004. Varieties of Sugar. — Several varieties of sugar 
are known; chief among vegetable sugars are cane 
sugar, or sucrose, and grape sugar, or glucose. Milk 
owes its sweetness to an animal sugar, called milk 
sugar, or lactose. All these sugars agree in having a 
sweet taste ; in having the atoms of hydrogen and oxy- 
gen present in proportion to form water, and in being 
susceptible of vinous fermentation. 

1005. Cane Sugar. (C 12 H u O n ). — This, the most im- 
portant variety of sugar, is chiefly obtained from the 
sugar cane; but the sugar maple and the beet root 
furnish a considerable quantity, as well as the date and 
cocoa-palms. It is contained in carrots and turnips, in 
the pumpkin, the chestnut, the stalks of maize, the ripe 
sorghum, and in a large number of tropical fruits ; in- 
deed, it is present in small quatities in the sap of most 
plants, and in all fruits and vegetables which are not 
acid to the taste. 

1006. Cane Sugar differs in its composition from 
starch, wood and gum, in containing a single additional 
molecule of water, while grape sugar con- 286 
tains four. It would seem from this com- /\ 
position, that it would be more easily pro- 
duced by artificial means from starch and 
similar substances. But this is not the fact. 



No modification of the process above described, has 

1004. W T hat are the properties of sugar ? 1005. What are the peculiari- 
ties of cane sugar ? 1006. What is said of cane sugar ? 



494 ORGANIC CHEMISTRY. 

as yet been devised by which starch and wood can be 
induced to take one additional atom of water, instead 
of four. Such a process would be a discovery of the 
greatest importance, as it would enable us to convert 
our potatoe and grain fields at will into sugar planta- 
tions, and make us independent of foreign supplies. 
The figure represents a crystal of cane sugar. The 
form belongs to the fourth system. 

1007. The general Character of Cane Sugar and 
its ordinary varieties are well known. It has a specific 
gravity of about 1.6. It dissolves in one-third its 
weight of cold water, producing the thick viscid liquid 
known as syrup. Under favorable circumstances it 
crystallizes, as shown in figure 286. Ordinary loaf 
sugar consists of a congeries of minute transparent 
crystals. "When two pieces of loaf sugar are rubbed to- 
gether in the dark, a pale violet phosphorescent light is 
emitted. At a temperature of about 320° cane sugar 
undergoes fusion, and on cooling forms a transparent 
amber colored solid. If the application of heat to 
melted sugar be continued, and it be gradually raised 
to 400°, or a little more, each molecule (C l2 H n On) of 
sugar loses two molecules of water, and a brown, nearly 
tasteless, mass remains, known as caramel, (C 12 H g 9 ). 
If caramel be heated beyond 420°, the compound is 
entirely decomposed, leaving a porous, brilliant mass 
of charcoal. 

1008. Production. — In manufacturing sugar from 

1007. What are the characteristics of cane sugar? 1008. How is cane 
sugar produced ? 



MOLASSES. 495 

the cane, the juice is first pressed out between heavy 
iron rollers, then clarified, and finally boiled down un- 
til it will crystalize on cooling. The granular crystals 
form the raw sugar ; the drainings, molasses. Lime is 
the principal agent in clarification. Its first effect is to 
neutralize the acid of the juice, which, as before seen, 
would gradually convert the cane sugar into grape 
sugar, and thus injure its quality. It also precipitates, 
with other impurities, the gluten, which, as will be 
hereafter seen, tends to produce more acid. The 
methods of producing sugar from the beet and maple 
are essentially the same. The final purification of 
sugar by bone black has already been described. 

1009. Molasses. — A large portion of sugar is ordi- 
narily lost in the form of molasses, from which it can- 
not be made to separate by crystallization. This is 
owing to the presence of impurities not separated by 
clarification which interfere with the process in a way 
not perfectly understood. A method has recently been 
contrived of avoiding the loss, and thus largely increas- 
ing the product of the beet and cane. Baryta added 
to the syrup combines with the sugar, and takes it to 
the bottom of the vessel as a solid compound of sugar 
and baryta, while the impurities remain behind. This 
precipitate is then removed and diffused in water. 
Carbonic acid being added, combines with the baryta, 
and leaves the sugar to form a pure and crystallizable 
syrup. Another method of increasing the product of 

1009. How may molasses be converted into sugar ? 



496 ORGANIC CHEMISTRY. 

sugar has been described in the section on sulphurous 
acid. 

1010. Grape Sugar. (C 12 H 14 14 .) This variety of 
sugar abounds in grapes, figs, plums, and some other 
fruits ; and constitutes the hard, granular, sweet masses 
found on these fruits in their dried state. As noticed 
in paragraph 998, it is also obtained by action of re- 
agents on starch ; on this account it is termed starch 
srigar. It results too from the natural process of ger- 
mination in which the starch of the seed under the in- 
fluence of diastase^ or decomposing nitrogenous matter, 
assimilates the elements of four molecules of water. 
The sweet taste of a sprouting grain of wheat or other 
cereal, affords a familiar illustration of this change. In 
France the production of this kind of sugar from starch 
is extensively carried oil as a commercial manufacture. 
Potato starch and sago are principally used. 

1011. Grape Sugar differs from Cane Sugar, in 
being less soluble in water and more soluble in alcohol. 
The former is less valuable than the latter, its sweetening 
power being as two of grape sugar to five of cane sugar. 
Sucrose crystallizes easily in prisms, but glucose crys- 
tallizes with difficulty in warty concretions composed 
of hard transparent cubes. 

1012. Glucose, or Grape Sugar, m the Animal 
System. — It makes its appearance in excessive quanti- 
ties in the blood and urine in a disease termed diabetes. 



1010. What is grape sugar? 1011. How does grape sugar differ from 
cane sugar ? 1012. Under what circumstances is sugar found in the ani- 
mal system ? 



ALCOHOL. 4:97 

It has been shown to be rapidly produced from one of 
the normal constituents of the liver. It has also been 
found, that by irritating with a needle the fourth ventri- 
cle of the brain of a dog or rabbit, grape sugar is devel- 
oped in the blood after a few minutes. 

AlcohoL (C 4 H 6 2 ). 

1013. Source astd Properties. — Alcohol is the pro- 
duct of the fermentation of sugar. It is a colorless, 
volatile, inflammable liquid, burning with a pale bluish 
flame, having an agreeable well-known spirituous odor, 
and an acrid burning taste. "When pure it has at 60° 
a specific gravity of 0.T938, boils at 173° ; it has never 
been frozen, though at a temperature of 166° below zero 
it becomes viscid. 

1014. Production from Sugar. — By the addition of 
brewers' yeast or some similar ferment to sugar, it is 
gradually converted into alcohol. Two molecules of 
water are separated in the process. One-third of the 
carbon and two-thirds of the oxygen which remain, 
pass off as carbonic acid gas, while alcohol is left. The 
yeast enters into no combination, and furnishes no 
material in the process. It acts merely by its presence 
to effect the decomposition, as will be hereafter ex- 
plained. 

1015. In this process of conversion, each molecule of 
sugar makes two of alcohol and four of the acid. The 

1013. What are the sources of alcohol ? 1014. How is alcohol produced 
from sugar ? 1015. Explain the diagram. 



ids 



ORGANIC CHEMISTRY. 




figure represents a molecule of grape sugar after tlie 
removal of two molecules of water. An arbitrary 
287 arrangement is given to the atoms 

for convenience of illustration. 
On striking off enough carbon and 
oxygen from the corners to make 
the required amount of carbonic 
acid, the residue may be supposed 
to fall apart into two molecules of 
alcohol. Alcohol is also produced 
from cane sugar by fermentation. The first stage in 
the process is its conversion, by yeast, into grape sugar. 
The latter is then changed into alcohol and carbonic 
acid, as above described. 

1016. Composition. — The composition of alcohol ap- 
pears sufficiently from the middle groups of the pre- 
ceding figure. According to the 
theory of compound radicals it is a 
hydrated oxide of ethyl. The prin- 
cipal group of the annexed cut, rep- 
resents a molecule of the radical ; 

the remaining circles stand for the oxygen and water 
with which it is combined in alcohol. 

1017. Production from Potatoes and Grain. — 
Where molasses or solution of sugar is the material 
used, alcohol is produced as already shown. But when 
potatoes and grain are employed as the material, a 
previous process is necessary by which the starch is 




1016. What is the composition of alcohol ? 1017. How is alcohol 
made from potatoes ? 



ALCOHOL. 499 

converted into sugar. This consists in the addition of 
bruised malt to the mashed potatoes or grain. The 
diastase of the malt has the effect of gradually trans- 
forming starch into sugar by its presence, as yeast con- 
verts sugar into alcohol. The mixture being kept at a 
temperature of about 140°, in a few hours the transfor- 
mation is complete. The starchy mixture has become 
sweet, and receives the name of wort. Brewers' yeast 
and water being then added to the wort, the conversion 
into alcohol commences. This is afterward separated 
from the water and refuse fiber of the potato or grain 
by the process of distillation, described in a subsequent 
paragraph. 

1018. Production from Illuminating- Gas. — Alco- 
hol may also be produced from heavy carburetted hydro- 
gen, one of the constituents of ordinary illuminating 
gas. This is one of the most remarkable results of 
modern science. Most of the processes of organic 
chemistry consist in taking apart the complex molecules 
of organic matter and reducing them to a simpler form, 
as was illustrated in the production of alcohol and car- 
bonic acid from sugar. Nature, for the most part, 
jealously withholds from man the power so to direct 
her forces as to "build tip and produce more complex 
organic substances by the combination of those of sim- 
pler nature. This takes place as a general rule only 
under the influence of the vital forces of vegetable and 
animal existence, as when the plant produces sugar 
from the elements of the atmosphere. 

1018. What is said of the production of alcohol from olefiant gas ? 




500 ORGANIC CHEMISTRY, 

1019. By reference to the central group of the figure, 
which represents a molecule of heavy carburetted hy- 
drogen, it will be seen that all that is necessary to effect 

its conversion into alcohol, is the 
addition of two molecules of water. 
By long agitation of the gas with 
strong sulphuric acid, the transfer- 
ence of part of the water which it 
holds combined is effected. On subsequent dilution 
and distillation, alcohol is obtained from the mixture. 
Carbonate of potassa is added in the process of distilla- 
tion, to diminish the proportion of w^ater which would 
otherwise pass off with the alcohol. After repeated 
distillation strong alcohol is thus obtained. 

1020. Distillation of Alcohol* — The process of 
distillation may be illustrated with the simple appara- 
tus represented in the fig- 
ure. On heating wine, cider 
or beer in the test-tube, its 
alcohol, which is more vola- 
tile than the water with which 

it is mingled, will be expelled as vapor and re-condensed 
as a colorless liquid. The cooler the vial is kept the 
more perfect is the condensation. For laboratory opera- 
tions the most convenient arrangement is a retort and 
condenser, as exhibited in figure 291. 

1021. Manufacturing Process. — The apparatus com- 
monly employed in the distillation of aldohol, consists 

1019. Explain its production. 1020. What is said of the process of 
distillation ? 1021. How is alcohol distilled on a large scale ? 




ALCOHOL. 



501 



of a large copper vessel in which the fermented wort is 
heated, and a long tube called the worm, in which the 
vapors are condensed. The worm is made to wind in 
a spiral, through a tub of cold water, that the conden- 
sation may be more completely effected. The spirit 
pours out at the lower end of the worm, where it 
emerges from the tub. It may be strengthened by re- 
peated distillation. Liebig^s Condensor, shown in Fig. 
291, is used for distillation in the laboratory. In order 
to obtain it entirely free from water, a highly rectified 
spirit is mixed with lime, or chloride of calcium, and re- 
distilled. These substances have such affinity for water, 
that they prevent its escape as vapor, while they in no 
wise effect the distillation of the alcohol. By this 
means pure alcohol, or absolute alcohol, is obtained. 



291 




1022. Uses of Alcohol. — Ordinary spirits of wine is 
a dilute alcohol containing but about seventy per cent, 
of absolute alcohol. The strongest alcohol known in 

1022. What is spirits of wine ? Mention some uses of alcohol. 



502 ORGANIC CHEMISTRY. 

commerce contains about 93 per cent, of alcohol and the 
balance water. Sometimes absolute alcohol is demanded 
for the chemist's use. Proof spirit is a mixture of equal 
parts of water and alcohol. The taste and odor of 
alcohol, its combustible character and action as a stim- 
ulus, are well known. It furnishes a cleanly fuel to the 
chemist and emits during its combustion a high tem- 
perature. It is a solvent of great value, dissolving 
readily resins, essential oils, iodine and a large number 
of bodies not soluble in water. It is largely used in 
medicine. Its solvent power renders it valuable in the 
preparation of medicinal extracts ; cologne and other 
perfumed liquids are produced through its agency. 

1023. Spirituous Liquors. — Spirituous liquors contain 
alcohol in large but varying proportions. They differ in 
their flavor according to the material from which they 
are produced. Brandy is distilled from wine, rum from 
fermented molasses, gin from a mixture of fermented 
rye and barley with juniper berries, and whiskey from 
malt liquors. The latter name is also given, in this 
country, to the liquor made from potatoes, corn, and 
rye. In Europe, the latter are more commonly called 
brandies. Some whiskeys which are characterized by a 
smoky flavor, had this communicated to them in the 
original manufacture by the smoke in the close apart- 
ments where they were prepared. This peculiarity is 
now conferred by the addition of a minute quantity of 
kreasote. 

1023. What is the source of the different spirituous liquors ? 



WINES. 503 

1024. Wines. — Wines are produced by the fermenta- 
tion of the juice of the grape. On exposure to the air, 
the gluten of the juice becomes a ferment, and causes 
the conversion of the sugar into alcohol. The addition 
of yeast is therefore unnecessary. This is also true of 
the juice of the apple, pear, and other fruits from which 
fermented liquors are similarly produced. The differ- 
ent kinds of w T ine owe their peculiarities chiefly to the 
variety of grape, the method of manufacture, and the 
chmate in which the grape is grown. The same variety 
of grape in different climates produces a wine having a 
different flavor. Even vineyards in the same locality 
yield wines peculiar to themselves. 

1026. Champagne. — Champagne and other sparkling 
wines owe their peculiarity to the presence of carbonic 
acid in large proportion. This is secured by allowing 
the last stages of fermentation to proceed in firmly 
corked bottles, so that all the gas which is evolved is 
retained. Or an ordinary wine is first produced by the 
usual process, and sugar and yeast are then added, to 
excite a new fermentation in the bottled liquid. 

1026. Alcohol in Wines. — "Wines differ in the 
amount of alcohol w T hich they contain ; from five per 
cent., in the weakest champagne, to twenty-five, in the 
strongest sherry. Those of southern climates are strong- 
est, because the grapes of those regions contain more 
sugar to undergo conversion into alcohol. Most wines 
also contain more or less acid and unfermented sugar. 

1024. How are wines produced ? 1025. How is champagne made ? 
1026. What is said of the proportion of alcohol in wines ? 



504 ORGANIC CHEMISTRY. 

1027. Flavor of Wines. — The wine flavor which be- 
longs to all wines, is owing to the presence, in extremely 
small portion, of an ethereal liquid called amantJiic ether. 
This substance does not exist ready formed in the grape, 
but is produced in the re-arrangement of atoms which 
takes place in fermentation. Its vinous odor, when 
separated from the wine, is most intense. It is prepared 
in Europe from grain spirit or cheap wines, and is used 
in this and other countries for producing imitations of 
wines of higher price. Potato whiskey is commonly the 
basis of these manufactured wines. Beside the general 
vinous flavor, different wines, like flowers, have an 
aroma or bouquet peculiar to themselves. These are 
owing to other and different flavoring substances, pres- 
ent in still smaller proportion than the oenanthic ether. 

1028. Tartar. — The improvement which age gives 
to wine is owing largely, not wholly, to the production 
of aromatic ethers as stated above. All wines are acid 
chiefly from the presence of the acid tartrate of potassa. 
During fermentation the bitartrate of potassa becomes 
less soluble, by reason of the production of alcohol and 
the acidity of the wine diminishes while its strength 
increases. This is deposited in the cask or bottle and 
is known as crude tartar or argol. It is from this circum- 
stance that grape juice alone is fit for making good 
wine ; when that of gooseberries or currants is used as 
a substitute, the malic and citric acids which those fruits 
contain cannot be thus withdrawn. Tartar consists of 

1027. What is said of the flavors of wines ? 1028. What acid is found 
in wine ? 



BEER AKD ALE. 505 

acid, tartrate of potassa, with a little tartrate of lime 
and coloring matter, and is the source of the tartaric acid 
of commerce. 

1029. Beer axd Ale. — Beer is the fermented extract 
of malted grain. The malt is prepared by softening 
barley in water, and then allowing it to sprout or germin- 
ate. Diastase^vhich is formed in the process of germ- 
ination, converts the starch of the grain into sugar, 
and thus prepares it for the subsequent process of fer- 
mentation. Yeast and hops are added to the extract 
of malt, which is called the wort, to bring about fer- 
mentation and help to give the product flavor. Ale is 
a similar malt liquor of different color. Porter is a 
darker variety of beer, made from malt which has been 
browned by roasting. 

1030. The juices of fruits containing sugar, when 
fermented, produce an alcoholic liquor strong in alcohol 
in proportion to the sugar present. Cider is from the 
juice of the apple, perry from the pear ; and nearly 
every fruit may be made to yield its own peculiar liquor. 
Even savage nations evince a knowledge of this fact. 
The nations of the islands of the Pacific when first 
visited, not only knew how to prepare an intoxicating 
liquor from the juice of the cocoanut but were accus- 
tomed to rectify it by a rude process of distillation. 

1031. Conversion of Alcohol into Ether. — Alco- 
hol is converted into ether by heating with oil of vitriol. 
To illustrate its preparation, equal volumes of strong 

1029. How are malt liquors prepared ? 1030. W^hat juices of fruits will 
produce alcohol ? 1031. How is alcohol converted into ether ? 



506 



ORGANIC CHEMISTRY. 




alcohol and oil of vitriol may be thoroughly mixed in 

a test-tube, and the vapors condensed in a cool vial, 

as represented in the fig- 
ure. A little sand may 
be added to the mixture 
with advantage. The vial 
should be- kept cool by 
means of paper repeatedly 
moistened during the pro- 
cess. The space between 

the tube and the neck of the vial should also be loosely 

closed with wet paper. 

1032. Explanation. — Alcohol is, as above stated, the 
hydrate of the oxide of ethyl. Sulphuric acid com- 
bines with the oxide itself, on heating, forming a 

bisulphate, and at a little higher 
temperature, yields it up again, as 
gaseous ether or oxide of ethyl. 
The change in the alcohol consists, 
simply, in the loss of an atom of 
water. The whole figure represents a molecule of alco- 
hol ; the lower portion one of ether. 

1033. Production of Ethyl. — The radical ethyl can- 

294 not, like many metals, be directly 

produced from its oxide. Heat, or 
fi\ other means, applied to accomplish 
this object, destroys the radical itself. 
But the end may be reached by a circuitous process. 




1032. Explain the above re-action. 1031. How is the radical ethyl pro- 
cured. 




PRODUCTS OF ALCOHOL. 507 

This consists in first producing from the oxide, an iodide 
of ethyl, and then removing the iodine by a metal. 
A colorless gas, of the composition indicated by the 
hydrogen and carbon atoms of the figure, is thus evolved. 

1034. Conversion of Alcohol into Olefiant Gas. 
— The production of olefiant gas from alcohol has been 
described in Section 584. The subject is again intro- 
duced for the purpose of illustrating the change, by 
reference to the atomic composition of the two substan- 
ces. Representing the atom of alco- 295 

hoi as before, it is converted by the 
removal of two atoms of oxygen, 
and two of hydrogen, into olefiant ® ®®®@ © 
gas. The composition of this gas is indicated by the 
central group of the annexed figure. The abstraction 
of oxygen and hydrogen is effected through the agency 
of the sulphuric acid used in the process. It will be 
observed that the radical ethyl, which has remained 
permanent in the changes before described, is here de- 
stroyed by the abstraction of a part of its hydrogen. 

1035. Conversion of Alcohol into Aldehyde. — 
Aldehyde (C 4 H 4 2 ) is a clear colorless liquid of a pecu- 
liar ethereal odor, produced by the ac- 296 

tion of the air or oxygen on alcohol. 

It is the product of a partial, slow 

combustion, or eremecausis of the 

alcohol, and forms the middle point 

in the conversion of alcohol into vinegar. It is for this 

reason that it is here introduced. 

1034. How is alcohol converted into olefiant gas ? 1035. What is aldehyde ? 




508 ORGANIC CHEMISTRY. 

1036. The two atoms of hydrogen which are burned 
out in the process, are indicated in the figure by smaller 
inscribed letters. By the removal, the radical ethyl is 
converted into the radical acetyl. Aldehyde is there- 
fore a hydrated oxide of acetyl. The characteristic 
odor of the substance is often perceived in the process 
for making vinegar. It may also be produced by de- 
pressing a wire gauze upon an alcohol flame, and there- 
by making the combustion incomplete. 

1037. Conversion of Alcohol into Vinegar. — If 
dilute alcohol is exposed to the air, it is converted, by 
oxidation, into acetic acid. Part of its hydrogen hav- 

297 ing been burned out to form alde- 

hyde, the oxygen acts further to oxi- 
dize the aldehyde which has been 
(W^^fifffi) (g) produced. The composition of each 
molecule is such as is represented in 
the preceding figure. It will be observed that the oxy- 
gen added is just sufficient to supply the place of the 
hydrogen removed in the formation of aldehyde. The 
latter substance being a hydrate of the protoxide of 
acetyl, acetic acid is a hydrated teroxide of the same 
radical. The presence of yeast or some other similar 
ferment, is essential in the production of vinegar as well 
as in that of alcohol. 

1038. Process of Manufacture. — A few years since, 
vinegar was exclusively produced by the souring of 
wine or cider. At present, large quantities are made 

1036. How is alcohol converted into aldehyde ? 1037. Explain the con- 
version of alcohol into vinegar. 1038. Describe the process. 






CHLOROFORM. 



509 



298 




from alcohol, by diluting it with, water, adding a little 
yeast, and then exposing it to the action of the air. 
This is best accomplished by allowing the diluted alco- 
hol to trickle through shavings packed in well ventila- 
ted casks, as shown in figure 298. A few 
passages through the cask suffice to 
convert the liquid into vinegar. The 
addition of yeast is unnecessary in pro- 
ducing vinegar from cider or wine, as 
these liquids contain a substance which 
acts as a ferment. The vapor of alco- 
hol may be readily converted into acetic 
acid by contact with platinum black. The property 
of platinum to produce oxidation in similar cases has 
been already explained. 

1039. Chloroform. (C 2 HC1 3 ). — Chloroform is best 
obtained by distilling pure alcohol with water and 
bleaching powder. Its molecule consists of two atoms 
of carbon, and one of hydrogen, combined with three 
of chlorine. The carbon and hydrogen atoms are re- 
garded as more intimately combined to form the radical 
formyl. Chloroform is therefore a terchloride of this 
radical. It is a colorless and volatile liquid, of a pecu- 
liar, sweetish smell. The inhalation of its vapor pro- 
duces insensibility to pain, and is much employed in 
surgical operations for this purpose. Ether has the 
same effect in a less degree. A mixture of the two is 
more commonly employed in this country. 



1039. How is chloroform prepared ? Mention its properties. 



510 ORGANIC CHEMISTRY. 

1040. Fusel Oil. — Fusel oil is a peculiar kind of 
alcohol, of extremely nauseous odor and poisonous prop- 
erties, which accompanies ordinary alcohol in its pro- 
duction from potatoes and grain. It may be separated 
by filtration through charcoal. But this process of 
purification is often neglected, and the fusel oil left to 
add its poison to the deleterious effects of the alcohol 
itself. It is this doubly poisonous alcohol which forms 
the basis of numerous manufactured liquors, wines and 
cordials. Fusel oil is the hydrated oxide of amyl, 
or amylic alcohol. This radical contains ten atoms of 
carbon to eleven of hydrogen. It is the last of the 
series of alcohols mentioned in Section 938. 

1041. Other Alcohols. — As indicated in the last 
paragraph, the term alcohol is used to designate other 
bodies than the ordinary vinous alcohol. The greater 
number of these have too little general interest to be 
introduced here. Besides the amylic alcohol men- 
tioned above, pyroxylic spirit, or methylic alcohol, is 
best known. 

1042. Methylic Alcohol. (C 2 H 4 2 ). — This alcohol is 
found among the products obtained by the destructive 
distillation of wood at a high temperature. It has 
many of the properties of ordinary alcohol, and in me- 
chanical and manufacturing processes it may be substi- 
tuted for it. In Great Britain it is largely used with 
the ordinary alcohol for the same manufacturing pur- 



1040. What is fusel oil ? Mention its properties. 1041. What is said 
of other alcohols ? 1042. How is methylic alcohol obtained, and how is 
it used ? 



ORGANIC ACIDS. 511 

poses. It is wholly unfit for use as a stimulating drink. 
Pyroxylic spirit is the hydrated oxide of methyl. 

1043. Ethers. — In chemistry the term ether has a 
wide signification. When unqualified by any other 
term it is understood to have reference to compounds 
described in a preceding paragraph as the oxide of 
ethyl. All the alcohols are made up on the same plan 
and are generally described as the hydrated oxide of 
some particular radicle. Each oxide of a radicle is an 
ether, so there are as many ethers of this kind as there 
are different alcohols. And acids combine with these 
ethers forming compound ethers, so that the number of 
ethers becomes immense. A few of the most interest- 
ing of these compounds will be noticed under the subject 
of artificial essences. 

Organic Acids. 

1044. A large number of acids of organic origin are 
known. About two hundred distinct acid compounds, 
products of the vegetable kingdom, have already been 
obtained. They are mostly composed of carbon, hy- 
drogen and oxygen, with the latter element generally 
in excess. They are for the most part solid and color- 
less, and many are crystalline. Some exist in the juices 
of plants and may be separated by simple processes. 
Tartaric and tannic acids are instances of this class, 
others are the result of natural decomposition or are the 
products of art. Acetic and pyroxyllic acids furnish 

1043. What are ethers ? 1044. What is said of the number and source 
of organic acids ? 



512 ORGANIC CHEMISTRY. 

examples in this connection. Others again exist in 
vegetable structures, and also may be produced by arti- 
ficial means. Oxalic and benzoic acids are instances of 
this kind. When existing in plants they are not usually 
free but are combined with potassa, soda or lime, form- 
ing salts with these bases. 

1045. Acetic Acid. (HO,C 4 H 3 3 ). — The production 
of this acid from alcohol has already been described. 
It is also a result of the destructive distillation of hard 
wood. An impure acid from this source, known asjpy- 
roligneoits acid, is largely used in the arts. Ordinary 
vinegar is a dilute acetic acid. It cannot be concentra- 
ted by evaporation, as the acid is volatile as well as the 
water which dilutes it. To obtain the strong acid re- 
course is had to the salts of acetic acid from which it is 
prepared by the method used for nitric and muriatic 
acids. It mixes with water at low temperatures in all 
proportions, and is commonly seen in its dissolved state. 
The pure acid may be obtained as a solid, but is a liquid 
at ordinary temperatures, and has a powerful and pecu- 
liar odor. It is entirely volatile and the vapor com- 
bustible. 

1046. Yinegar. — The dilute acetic acid used for do- 
mestic purposes varies in quality according to the source 
whence it is obtained. Cider, wine and beer furnish 
vinegar by the change which the alcohol they contain 
undergoes, this alcohol by oxidation becoming acetic 
acid. Saccharine liquids also produce vinegar by the 

1045. How is acetic acid obtained ? 1046. What acid is contained in 
vinegar ? 



VIXEGAE, 513 

sugar which they contain being converted into alcohol, 
and this alcohol ultimately into acetic acid. Common 
vinegar usually contains from three to five per cent, of 
acetic acid, with a small amount of nitrogenous anf 
coloring matters. Acetic acid dissolves many organi 
substances, such as gluten, gelatin, gum, resins, ttu 
white of eggs, etc., hence the use of vinegar in moderat 
quantities promotes digestion. 

1047. Deteriorations" of Yixegar. — Yinegar oft 
becomes the home of animal and vegetable life. It is 
apt to be infested with flies, {Musca cellarus), and by 
animalcules, commonly termed eels (Yibriones aceti). 
These may be destroyed by heating the liquid. When 
vinegar is exposed to the air it gradually becomes turbid 
or mother y, losing its acidity and depositing a gelatinous 
conferva, the vinegar plant. The vinegar becomes weak 
as this growth increases, the acetic acid being assimila- 
ted by the plant. The popular idea that this gelatinous 
mass, termed the mother of vinegar, promotes the pro- 
cess of change and adds strength to vinegar, is correct 
only in this, that it holds vinegar like a sponge, and 
when placed in an alcoholic or saccharine liquid it in- 
duces acetous fermentation from the vinegar that is pres- 
ent. A crumb of bread soaked in vinegar would be 
equally serviceable. 

1048. Acetates. — The salts formed by the union of 
acetic acid with bases are numerous, and many of them 
of much importance in the arts. Acetate of lead is 

1047. How does vinegar deteriorate ? 104S. Mention some of the 
acetates. 



514 ORGANIC CHEMISTRY. 

perhaps as well known as any of this class of salts. 
When oxide of lead is dissolved in excess of acetic acid 
and the filtered liquid is evaporated, prismatic crystals 
are obtained having the composition PbO,C 4 H 3 3 + 
3HO. This salt is popularly known as sugar of lead. 
A solution of the tribasic acetate (3PbO,C 4 H 3 3 ) is 
known in pharmacy as Goulard? s Extract of Lead. It is 
applied as a cooling lotion to sprains and bruises. Ace- 
tate of Ammonia has long been used in medicine under 
the name of Spirit of Minder erus. Acetate of Potassa, 
a very deliquescent salt is of great value in medicine. 
Acetate of Soda is largely manufactured as a source of 
acetic acid. Acetates of Alumina are extensively used 
as mordants by calico printers. Peracetate of Iron is 
used by dyers and calico printers. Acetates of Copper 
are valuable as pigments and constitute the varieties of 
verdigris. 

1049. Oxalic Acid. (HO,C 2 3 ).— This acid, one of 
the earliest isolated by chemists, is found ready formed 
in the juice of the varieties of sorrel and rhubarb, in 
several other plants and in some fruits ; in these it is 
generally combined with potassa or lime. Certain lich- 
ens, growing upon calcareous rocks, contain half their 
weight of oxalate of lime. In combination with iron 
it is found as a mineral. It is also produced by the ac- 
tion of reagents on a variety of organic matter. 

1050. Character and Uses. — The ordinary crystals 
of oxalic acid (HO,C 2 3 + 2HO) are transparent, four 
sided prisms, not unlike epsom salt in appearance, for 

1049. How is oxalic acid found? 1050. For what is it used? 



OXALATES. 515 

which it is sometimes mistaken. They are intensely 
sour, dissolve readily in cold water, and more largely 
in hot water. Unlike other vegetable acids, oxalic acid 
is a powerful poison ; a dose of it having destroyed life 
in ten minutes. The antidote is chalk or magnesia 
suspended in water. The crystals, when heated, volati- 
lize without combustion and without leaving any car- 
bonaceous residue. It is extensively employed in calico 
printing and dyeing, and to some extent in bleaching 
and cleansing straw goods. In chemical analysis it is 
used as a test for detecting the presence of lime. 

1051. Artificial Production. — The natural sources 
of oxalic acid do not supply the demand and recourse 
is had to its artificial production. Its formation from 
woody fiber was noticed in Paragraph 964. One manu- 
facturing establishment in Manchester, England, pro- 
duces nine tons of oxalic acid weekly from sawdust. 
Oxalic acid is manufactured in large quantities for com- 
merce by the action of nitric acid on sugar, starch and 
dextrin. Instead of adding the nitric acid directly to 
the sugar or other organic compound, a mixture of salt- 
peter and oil of vitriol is used, and the nitric acid is 
evolved from the saltpeter by the action of the sulphu- 
ric acid during the process of manufacture. The result 
is the production of oxalic acid and sulphate of potassa. 
These may be readily separated. 

1052. Oxalates. Oxalate of Ammonia is a valuable 
reagent in chemical analysis, being used much more 

1051. How is oxalic acid manufactured ? 1052. Mention some of the 
oxalates. 



516 ORGANIC CHEMISTRY. 

frequently than oxalic acid itself in the detection and 
separation of lime. Oxalates of Potassa are common 
salts. The binoxalate, known as the salt of sorrel, is 
obtained from the juice of wood-sorrel to which it gives 
its sour taste. It is sometimes used for the removal of 
ink-stains and iron-rust from linen. Oxalate of Lime 
is the white solid formed whenever a solution of oxalic 
acid or an oxalate is added to a soluble salt of lime. It 
exists also in many plants and often accumulates in the 
cells and occasionally floats in the juices in the form of 
minute crystals, known as r aphides. This salt exists 
occasionally in the human urine and forms stony con- 
cretions, called mulberry calculi. The other salts of 
oxalic acid are not of general interest. 

1053. Tartaric Acid. (2HO,C 8 H 4 O 10 ).— This acid is 
found free, but more frequently in combination in many 
vegetables. It is the acid of the tamarind, the pine 
apple and several other fruits, but exists most abund- 
antly in the juice of the grape, which is its principal 
source. It exists here as the acid or bitartrate of potassa. 
It is occasionally met with in combination with lime, 
forming the tartrate of lime. It may be separated 
from its combinations and obtained as a colorless solid. 

1054. Character and Uses. — Tartaric acid forms 
translucent or transparent crystals, often of a large size, 
which are very sour. When highly heated the acid 
fuses and burns, evolving a peculiar odor and leaving a 
slight residue of carbon. Mixed with bicarbonate of 

1053. How is tartaric acid obtained ? 1054. For what is tartaric acid 
used ? 



TARTRATES. 517 

soda, tartaric acid forms a compound used as an effer- 
vescing draught. It is used to some extent in domestic 
cooking. But by far the greatest application is in calico 
printing, for which, purpose large quantities are con- 
sumed. In the laboratory it is used as a test for potassa 
and to prevent the precipitation of certain oxides. It 
is also used in the separation of the newly discovered 
metals caesium and rubidium. 

1055. Tartrates. — There is a large number of salts 
of tartaric acid, most of which may be obtained in a crys- 
talline condition. The most common of these are those 
used in medicine. Tartrate of potassa (2KO,C 8 H 4 O 10 ) 
is an artificial crystalline salt, readily soluble in water 
and has a saline and bitter taste. Bitartrate of potassa 
or acid tartrate is the salt that exists in the juice of the 
grape. On fermentation of the juice it is deposited in 
the wine casks as a white or red crystalline incrusta j 
tation, called argot or crude tartar. Pipe-clay added 
in small proportion to the solution of the crude tartar 
in boiling water absorbs the coloring matter and takes 
it to the bottom as a sediment. The purified crystals 
afterwards appear upon the surface of the liquor, and 
upon the sides and bottom of the boiler, which are 
popularly known as cream of tartar ', a term which was 
originally applied to the partially crystallized surface 
mass. Tartrate of potassa and soda (KO,NaO,C 8 H 4 O 10 
+ 8HO) is known under the name of Rochelle salts. 
Tartrate of potassa and antimony (KO,SbO 3 ,C 8 H 4 O 10 + 

1055. Mention some of the tartrates and their uses. ' 



518 ORGANIC CHEMISTRY. 

HO) is the tartar emetic or tartarized antimony of phar- 
macy. 

1056. Citric Acid. (3HO,C 12 H 5 O n ).— This acid" is 
found abundantly in the juice of lemons and limes, 
from which it is prepared for commerce. It exists also 
in many other fruits, as the orange and cranberry, and 
in connection with another acid, malic, in our small 
fruits, as the currant, gooseberry, etc. Citric acid forms 
colorless, prismatic crystals, w T hich have an agreeably 
acid taste, and are very readily soluble in water. Citric 
acid is used in the preparation of acid drinks and in 
pharmacy as a substitute for lemon-juice. Like tartaric 
acid it is used in calico-printing. The citrates of potassa, 
soda, ammonia, iron and magnesia, are of value in 
medicine. 

1057. Malic Acid. (2HO,C 8 H 4 8 ),— This acid was 
first obtained from the juice of the apple, but is now 
known to be extensively diffused through the vegetable 
kingdom. It is present in most acidulous fruits, and is 
often accompanied by citric acid. It is now chiefly ex- 
tracted from the unripe berries of the mountain ash. 
Malic acid is obtained in crystals with difficulty and 
when in solution, unless quite pure, is liable to undergo 
decomposition. 

1058. Tannic Acid. (C 54 H 22 3 4). — Tannin, or tannic 
acid, exists in nut-galls and in the bark and leaves of 
many trees. It is the principle which imparts to them 



1056. Where is citric acid found ? For what is it used ? 1057. Where 
is malic acid procured ? 1058. Mention the source and properties of 
tannic acid. 



INK. 519 

their astringent taste, and gives to the tan liquor the 
property of converting hides into leather. When sepa- 
rated from the other substances with which it is com- 
bined in nature, it is a yellowish, gummy mass. It is 
soluble in water, and possesses the property of precipi- 
tating glue or gelatin, and many metallic oxides. 

1059. Writing Ink. — Common writing ink is pre- 
pared from nut-galls and proto-sulphate of iron. When 
first made, it is principally a tannate of the protoxide 
of iron, and forms a very pale solution. Be- 
fore it is fit for use, it must be exposed for a 
time to the air, and thereby converted, par- 
tially, into tannate of the peroxide. This is a 
bluish black precipitate, and imparts to it the 
requisite color. It is essential to the perma- 
nence of ink, that the change should take place, in part, 
in the fiber of the paper itself. Too long exposure 
should, therefore, be avoided in the manufacture. The 
pale ink thus produced, which blackens further in using, 
is much more permanent than a thicker, darker ink, 
produced when this caution is not observed. 

1060. Six parts of nut-galls to four of copperas, are 
found to be the best proportions for producing a perma- 
nent ink. The galls are to be boiled with water, the 
decoction strained, and mixed with copperas solution. 
Gum and cloves are added, the former to keep the color- 
ing matter of the ink from settling, and the latter to 
prevent its moulding. After a ripening of a month or 

1059. What is the coloring matter of writing ink ? 1060. Give the pro- 
cess of its preparation. 




520 ORGANIC CHEMISTRY. 

more the liquid is strained. The coloring matter of ink 
is immediately produced in a solution of copperas, as a 
bulky precipitate, by the addition of tincture of galls 
and a little nitric acid. 

1061. Gallic Acid. (C 14 H 6 O 10 ). — This acid is found 
in small quantities in connection with tannic acid in 
nut-galls, in sumach, and in a large number of astrin- 
gent vegetables. It may be obtained from tannic acid ; 
this latter acid, when dry, remains unchanged, but when 
moist, or in solution, it absorbs oxygen and passes into 
gallic acid. Gallic acid is white and crystalline, soluble 
in water and alcohol. Like tannic acid, when heated 
in the air, it melts and burns like a resin. "With the 
salts of the peroxide of iron it produces a blue-black 
precipitate ; it does not precipitate gelatin. 

1062. Pyrogallic Acid. (Crusoe). — This substance 
is manufactured in large quantities for the purposes of 
photography. It is obtained by sublimation of gallic 
acid which, when at a temperature between 410° and 
420°, is volatilized and converted into carbonic and 
pyrogallic acids. The pyrogallic acid thus produced 
forms brilliant crystalline plates, is freely soluble, very 
feebly acid, and of an astringent, bitter taste. An alka- 
line solution of this acid absorbs oxygen gas very read- 
ily, and is used in chemical analysis for the purpose of 
determining the amount of oxygen in a mixture of gases 
where this element is present. But its most extensive 
application is in photographic operations, for the pur- 

1061. What are the properties of gallic acid ? 1062. How is pyrogallic 
acid obtained ? For what purpose is it used ? 



CYANOGEN. 521 

pose of developing the latent image upon the collodion 
film containing the silver salt, after it has been exposed 
to the action of light. 

1063.^ Cyanogen. (]STC 2 or Cy). — Before proceeding 
with the description of hydrocyanic, or prussic acid, the 
production of cyanogen, which en- 300 

ters into its composition, will be 
briefly considered. Cyanogen is 
a colorless gas, with a peculiar 
odor resembling that of peach pits. 
It is nearly twice as heavy as at- 
mospheric air. It burns with a 
beautiful purple flame. Cyano- 
gen is a compound radical, pos- 
sessed of important analogies to 
chlorine and the other electro-jiegative elements. Its 
molecule contains one atom of nitrogen and two of 
carbon. 

1064. Production. — Cyanogen may be expelled from 
the cyanide of mercury by the agency of heat. This 
metal retains cyanogen as it does oxygen, but feebly. 
A method more commonly employed is to produce and 
decompose the cyanide of mercury at the same moment. 
This is effected by mixing chloride of mercury ; to fur- 
nish the metal, with the double cyanide of iron and 
potassium, which furnishes the cyanogen. The other 
elements unite to form chlorides of iron and potassium, 
while the cyanide of mercury is decomposed as fast as 

1063. Mention the composition and properties of cyanogen. 1064. 
How is cyanogen prepared ? 




522 ORGANIC CHEMISTRY. 

it is formed. The double cyanide of iron and potas- 
sium, above referred to, is the commercial yellow prus- 
siate of potash. Two parts of this salt are to be heated 
with one of chloride of mercury, in the above process. 
The prussiate cannot be used alone for the production 
of cyanogen, on account of the firm retention of this 
radical by the highly electro-positive metals which enter 
into the composition of the salt. 

1065. Cyanide of Potassium. (KCy). — Cyanide of 
potassium is a white substance, resembling porcelain in 
appearance, and quite soluble in water and alcohol. It 
is largely employed in preparing solutions of the pre- 
cious metals, for galvanic gilding and silvering. It is 
produced on a large scale, by fusing together carbonate 
of potash and refuse animal matter. The latter fur- 
nishes the carbon and nitrogen required for the produc- 
tion of cyanogen, while the carbonic acid and oxygen of 
the salt, are principally evolved as oxide of carbon. 
The cyanide of potassium is best extracted from this 
residue by alcohol, which leaves the other material un- 
dissolved. 

1066. Prussiate of Potash. (K 2 FeCy 3 =K 2 Fcy).~ 
Cyanide of iron is always incidentally formed from the 
iron of the vessel in the above process. If water is 
added to the fused mass, both cyanides dissolve ; al- 
though the latter, when alone, is entirely insoluble. 
Prom the solution, the double cyanide of potassium 
and iron, mentioned in a preceding paragraph, is ob- 

1065. How is cyanide of potassium prepared? Mention its uses. 
1066. How is yellow prussiate of potash prepared ? Mention its uses. 



FERR0 CYANIDES. 523 

tained, by evaporation, in splendid yellow crystals. It 
is known in commerce as yellow prnssiate of potash, 
and is largely used in the arts for the production of 
prussian blue (Fe 4 Fcy 3 ), and cyanide of potassium. 
Prussian blue is obtained by adding its solution to a 
salt of the peroxide of iron. As any solution of iron 
is readily peroxydized by the addition of a little nitric 
acid, the yellow prussiate may be employed as a test for 
this metal. 

1067. Ferrocyaotdes. — The yellow prussiate of pot- 
ash, produced as above described, is not properly a 
double cyanide of iron and potassium. There is reason 
to believe that the cyanogen is more intimately com- 
bined with the iron than such a name would imply. It 
seems to have lost its ordinary properties in the com- 
pound. Neither the alkalies or sulphide of ammonium, 
which usually precipitate iron from its solutions, have 
any power to precipitate it from this salt. The three 
molecules of cyanogen, which enter into its composi- 
tion, seem to have hidden and absorbed it. They have 
formed with it, indeed, a new compound radical, called 
ferrocyanogen, (FeCy 3 =Fcy). The double salt above 
mentioned is therefore more properly a ferrocyanide of 
potassium. Ferrocyanogen, like all other compound 
radicals, conducts itself, under ordinary circumstances, 
as an elementary substance. 

1068. Ferricyanogen. — On the removal of one atom 
of potassium from two molecules of the prussiate of 

1067. What is said of ferrocyanogen ? 1068. What is ferrieyanogen ? 



524: ORGANIC CHEMISTEY. 

potash, a coalescence of the ferrocyanogen of the two 
molecules seems to be the result, and a new compound 
radical is formed. This radical is called ferricycmogen, 
(Fe 2 Cy 6 =Fdcy). It combines with the three remaining 
atoms of potassium, to form ferricyanide of potassium, 
(KsFdcy). 

1069. Prussic Acid. (HCy). — Hydrocyanic acid is 
made from cyanide of potassium, by the same method 
employed for producing hydrochloric acid from common 
salt. The ferrocyanide of potassium is more commonly 
employed in the process. Prussic acid is intensely 
poisonous. A drop or two of the concentrated liquid, 
placed upon the tongue of a dog, produces immediate 
death. On account of its extremely dangerous proper- 
ties, the preparation of the acid should never be at- 
tempted except by a professional chemist. The odor 
of the acid is somewhat similar to that of cyanogen, 
and may be frequently detected in the vicinity of estab- 
lishments where galvanic gilding is conducted. Ferro- 
cyanogen and ferricyanogeii, like simple cyanogen, have 
their hydrogen acids and series of salts. The acid of 
the former is bibasic, and that of the latter tribasic, as 
already shown by the composition of their potassium 
compounds 

Organic Bases. 

1070. Alkaloids. — Morphine and strychnine, the 
former a useful medicine, and the latter, the most dread- 

1069. Give the properties of prussic acid and its mode of preparation. 
1070. Give the names of some of the alkaloids. Why are they so called ? 



ALKALOIDS. 525 

ful of poisons, are examples of the alkaloids. They 
are white crystalline bodies but slightly soluble in water. 
Most of them contain the four organic elements, and 
they possess a positive chemical character of great 
activity. They are called alkaloids from their resem- 
blance, in certain properties, to the alkalies of inorganic 
chemistry. Their action upon vegetable colors is the 
same ; like the alkalies, they also form salts with both 
organic and inorganic acids. They are, in fact, true 
alkalies. Their alkaline property does not, however, 
seem to depend on the oxygen which they contain. 
Some of them, indeed, do not contain this element. It 
is highly probable that certain of the alkaloids belong 
to the class of compound ammonias mentioned in the 
first Chapter of Organic Chemistry. 

1071. Their action on the human body does not de- 
pend upon their alkaline character, but on the other 
and peculiar properties belonging to each. The salts 
of the alkaloids are generally preferred in medicine, in 
view of their ready solubility. In large doses they are 
all poisonous. The tincture of nut-galls is employed as 
an antidote, because of the property of the tannic acid 
which it contains, to form with most of the alkaloids 
insoluble precipitates. 

1072. Occurrence. — Morphine is contained in opium, 
quinine is extracted from Peruvian bark, and strychnine 
from the nux vomica. The latter is also the poison of 
the celebrated upas. Theine and nicotine are other 

1071. What is their action on the hnman body? Their antidote? 
1072. What is the sonrce of the alkaloids ? 



526 ORGANIC CHEMISTRY. 

alkaloids, the former of which is found in tea and coffee, 
and the latter in tobacco. Theine may be obtained, as 
a sublimate of silky crystals, by moderately heating tea 
in an iron pot covered with a paper cone. 

1073. Preparation. — Most of the alkaloids may be 
extracted from the material which contains them by 
means of acidulated water. A salt of the alkaloid is 
thus obtained in solution. From this salt the alkaloid 
may be precipitated, like oxide of iron or any other 
base, by ammonia. Nicotine is a most energetic poison, 
falling scarcely below prussic acid in its destructive 
properties. 

Essential Oils and Resins. 

1074. Yolatile or Essential Oils. — Oils of tur- 
pentine and lemon, and otto of roses, are examples of 
essential oils. They are almost as various as plants 
themselves, and may be regarded as the odorous prin- 
ciple of plants. They are mostly characterized by a 
strong aromatic odor and a pungent burning taste. 
Dropped on paper they give a stain, but this disappears 
after a little time ; they volatilize, hence the distinctive 
name volatile oils. They dissolve in alcohol, forming a 
class of substances known as essences^ whence comes 
the name essential oils. They have not the greasy feel 
of fatty oils, nor do they form soaps with alkalies. By 
oxidation they are converted into resins. 



1073. How are the alkaloids extracted ? 1074. What are the properties 
of essential oils ? 



to 



ESSENTIAL OILS AND RESINS. 527 

1075. Occurrence. — The essential oil is not generally 
diffused uniformly through, the plant, but is found most 
largely in some particular part. The rose, violet, and a 
large number of plants, yield an essential oil from the 
petals of the flower ; mint and thyme from the leaves and 
stalk ; cedar and pine from the wood ; vanilla and cara- 
way from the seed ; cinnamon from the bark ; and gin- 
ger from the root. Sometimes different oils are found 
in different parts of the same plant ; thus with regard 
to the orange tree, the leaves, flower and fruit each 
yield a distinct oil. 

1076. Preparation. — The oil is generally obtained 
by distilling portions of the plant with water. The 
volatile oil passes over with the steam and floats upon 
the condensed liquid in the receiver. Oil of turpen- 
tine is thus made from the common turpentine or pitch, 
as it is sometimes called, which exudes from the pine ; 
ordinary rosin remains behind. In some cases the oil 
is pressed from the part of the plant containing it, as 
from orange and lemon peel. The delicate perfume of 
violets and other flowers which contain but a small por- 
tion of essential oils is extracted by mingling the flow- 
ers with lard. This substance has the property of 
absorbing the oil and yielding it again by distillation or 
solution in alcohol. In a few cases the oil is not found 
ready formed in the plant but is generated by the action 
of water upon peculiar principles, as in the production 
of oil of bitter almonds. There ~are a few instances of 
artificial production. 

1075. Where do they occur ? 1076. How are they procured ? 



528 ORGANIC CHEMISTRY. 

1077. Uses of the Essential Oils. — The essential oils 
are extensively used for many purposes; some in the 
manufacture of paints and varnishes, some for burning 
in lamps, some in medicine, and others in perfumery. 
Essences, perfumes, and cordials are solutions of certain 
of these oils in alcohol, with the addition in the case of 
cordials of a portion of sugar. In the preparation of 
perfumery, a single oil is rarely used by itself; a better 
result is obtained by skillful admixture of many. 

1078. Composition. — The oils generally contain two 
proximate principles, one a solid, stearopten, the other 
a liquid, elaiopten y at common temperatures the latter 
holds the former in solution, but if cooled slowly the 
stearopten, which is a species of camphor, is usually 
deposited. Many of the essential oils are composed 
wholly of carbon and hydrogen, others contain oxygen 
in addition to these elements, and others sulphur. 

1079. Oils composed of Carbon and Hydrogen. — 
This division includes many of the most common and 
most valuable of the essential oils. They have for the 
most part an identical chemical composition, which is 
expressed by the formula C 20 H 16 . The oils of orange, 
lemon, turpentine, pepper, juniper, parsley, citron, bur- 
gamot, caraway and others, however widely they differ 
in properties, have the same elementary composition 
and are isomeric. The oil of turpentine may stand as 
the representation of this class. It has a specific gravity 
of 0.864, boils at 320, is but slightly soluble in water, 

1077. What are the uses of essential oils ? 1078. What is their compo- 
sition ? 1079. What is said of the composition of essential oils ? 



BURNING FLUID. 529 

is readily soluble in alcohol, ether and the fixed oils. 
It has great solvent power, dissolving sulphur, phospho- 
rus, caoutchouc, etc., readily. It is extensively em- 
ployed as a solvent of resins in the manufacture of 
varnishes. Under the name of campheue it was formerly 
largely used as a source of light, but has been mostly 
superseded by the mineral oils. 

1080. Bursting- Fluid. — "Burning fluid," so called, 
is a solution of camphene or rectified turpentine in 
alcohol. The sole object of the camphene is to increase 
the proportion of carbon, and thus render the flame 
more luminous. Unmixed camphene may also be 
burned in lamps provided with tall chimneys. The 
effect of the chimney is to make a strong draft, and 
thus provide a liberal supply of oxygen in proportion 
to the large amount of carbon which the liquid contains. 
Without this provision, camphene burns like camphor, 
with much smoke, depositing a large part of its carbon 
in the form of soot or lamp-black. 

1081. Burning Fluid, "explosive." — The mixture 
of alcohol and camphene, known as burning fluid, is 
commonly spoken of as explosive. That this is not the 
fact, may be readily shown by pouring a little in a saucer 
and inflaming it. It burns, under these circumstances, 
as quietly as from the wick of a lamp. But if a can, 
containing burning fluid, be shaken up and then emptied 
of its liquid contents, it is found to contain an explosive 
atmosphere. To prove this, it may be tightly corked 

1080. What is the composition of " burning fluid ?" 1081. What is said 
of the explosibility of "burning fluid f" 



530 ORGANIC CHEMISTRY. 

and fired through a small hole punched in the side. On 
applying a lighted taper to the opening, the can ex- 
plodes with a loud report, and is torn to pieces by the 
force of the escaping gases. The small proportion of 
fluid remaining in the can, after every drop that can 
be poured out is removed, is sufficient to produce this 
effect. • 

1082. Explanation. — The principle of the explosion 
is precisely the same as that involved in the same ex- 
periment with hydrogen and air. The only variation 
consists in the substitution of the combustible vapor of 
alcohol and camphene, for hydrogen gas. It is the mix- 
ture of alcohol vapor and air, to which the effect is to 
be principally ascribed ; the experiment may be made, 
indeed, as well with unmixed alcohol, or ether, as with 
burning-fluid. It may also be made with camphene, 
but in this case the vessel must be warmed, in order to 
vaporize the liquid in sufficient quantity. 

1083. The above experiment may be performed with 
safety, in an open vial, by vaporizing a drop or 
two of either of the above liquids within it, 
and then applying a lighted taper to the mouth, 
in this case, the appearance of flame at the 
mouth of the vial, and a rushing noise, is all 
that is observed. This experiment will enable 
the student to disprove the alleged umexplosive 

character of certain fluids in use for purposes of illu- 
mination. In moderately warm weather it is sufficient 

1082. W T hat is the cause of the explosion ? 1083. Describe another 
form of the experiment. 



CAMPHORS. 531 

to fill the vial, and then to empty it, in order to form 
the explosive atmosphere. 

1084. Oils containing Oxygen. — The essential oils 
of this kind are numerous and include the oil of bitter 
almonds, cinnamon, aniseseed, peppermint, wintergreen 
and others, with camphor and its modifications. The 
composition of these substances is various. They are 
used mostly in medicine and perfumery. 

1085. Camphors. — These are concrete, volatile oils, 
containing oxygen ; as previously stated, several of the 
oils when exposed to a low temperature, deposit solids. 
These are white and crystalline, and are frequently 
isomeric with the oils themselves. Common camphor 
is obtained from the Laitrus Camphora of China and 
other Eastern countries, by distillation with water. It 
is afterwards purified by sublimation. It dissolves 
readily in alcohol, forming spirits of camphor. Its 
volatile character is the occasion of a singular appear- 
ance, when small bits of the substance are thrown upon 
warm water. The particles are seen to sail about as if 
they were possessed of life, owing to the propelling 
effect of the vapor which escapes beneath them. The 
composition of common camphor is C^H^O^ Ar- 
tificial camphors, are produced by the action of dry 
hydrochloric acid gas upon camphene. One of the 
compounds so formed has the composition C 20 H 16 IIC1, in 
which hydrogen and chlorine supply the place of the 
two atoms of oxygen in the ordinary camphor. This 
compound is a white crystalline substance, having an 

1084. What oils contain oxygen ? 1085. What are camphors ? 



532 ORGANIC CHEMISTRY. 

aromatic odor and taste resembling that of gum cam- 
phor. 

1086. Oils containing Sulphur. — This class of essen- 
tial oils is more limited in number than the preceding. , 
They are noted for their acrid, burning taste, and also 
for their peculiar unpleasant odor, which may be readily 
noticed in the breath after eating substances containing 
them. Onions, garlic, horseradish, assafoetida, black 
mustard, etc., furnish oils belonging to this class. The 
seeds of both black and white mustard yield on pressure 
a large quantity of a bland fixed oil, but they do not con- 
tain any essential oil ready formed. The seed of the 
black mustard, however, when crushed and moistened 
with water, undergoes a kind of fermentation, during 
which an essential oil is developed, which may be ob- 
tained by subsequent distillation. This is a colorless 
oil, has the composition C 8 BVN~S 2 ; possesses a painfully 
penetrating odor, which produces a flow of tears, and 
when applied to the skin raises a blister. 

1087. Artificial Essences. — Many of the essential 
oils are compounds of organic acids and bases. Several 
of them may be artificially produced. Pine apple oil 
is a compound of butyric acid with ether or oxide of 
ethyl. The butyric acid of the compound may be pre- 
pared from rancid butter or by fermenting sugar with 
putrid cheese. Bergamot pear oil is an alcoholic solu- 
tion of acetates of the oxide of ethyl with acetate of 
oxide of amyl. The latter is the ether of the nauseous 

1086. What is said of oils containing sulphur ? 1087. What is said of 
artificial essences? 



oils. 533 

and poisonous fusel oil, which has before been men- 
tioned. 

1088. Apple oil is a compound of valerianic acid with 
the same ether. The valerianic acid of the compound 
is also made from fusel oil. Oil of grapes, and oil of 
cognac, used to impart the flavor of French brandy to 
common alcohol, come from the same source. Oil of 
winter-green may be prepared from willow bark and 
wood vinegar. Oil of hitter almonds is prepared from 
coal tar. These artificial essences, although produced 
in several cases from poisonous substances, may be used 
as flavors with perfect safety. It is highly probable, and 
in many cases certain, that the flavor of the fruits them- 
selves, is owing to the presence of these precise com- 
pounds in small quantities. 

1089. Empyreitmatic Oils. — The volatile oils which 
are produced by the destructive distillation of vegetable 
and animal substances receive this general name. The 
oils of wood and coal tar are examples. Another em- 
pyreumatic oil is produced in the combustion of tobacco 
in ordinary pipes. This oil is extremely poisonous. It 
is to be understood that these oils do not exist ready 
formed in the substances from which they are obtained, 
but are produced in the re-arrangement of atoms which 
takes place when organic bodies are subjected to a high 
temperature. 

1090. Resists. — The resins, of which ordinary pine 
rosin may serve as an example, are formed by the action 

1088. What is artificial apple oil ? Artificial oil of bitter almonds ? 
1089. What are empyreumatic oils ? 1090. How are resins formed ? 



534 ORGANIC CHEMISTRY. 

of oxygen upon the essential oils. Oil of turpentine 
may be thus partially converted into resin by long ex- 
posure to the air. On subsequently heating it, only a 
portion is found to be volatile, while a resinous mass 
remains behind. Turpentine, or pitch of pine trees, is 
thus formed in nature from the oil of turpentine as it 
exudes from the trees. But the conversion is only 
partial, so that the turpentine yields, on distillation, a 
portion of oil, while rosin remains behind. Resins are 
easily distinguished from gums by their insolubility in 
water ; they are, on the other hand, readily soluble in 
alcohol or ether. They are not liable to decay, like 
most other substances of vegetable origin. Copal shel- 
lac, mastic and amber are all resins. The latter is 
found in certain coal mines and at the bottom of the 
sea, and has probably had its origin in the forests of 
some primeval age. 

1091. Explanation. — The action of the oxygen of 
the air in the above case is similar to that which occurs 
in the conversion of alcohol into vinegar. A portion of 
the hydrogen is burned out, as it were, and removed 
in the form of water, while another portion of oxygen 
takes its place. 

1092. Use of -the Eesins — Varnishes. — The resins 
are principally employed for the production of varnishes. 
These are simply solutions of resins in alcohol, ether, 
or spirits of turpentine ; or an intimate mixture of the. 
latter with fused resin and oil. In preparing copal var- 

1091. Explain the above transformation. 1092. What use is made of 
the resins ? How are varnishes made ? 



RESINS. 535 

nish, which is the most brilliant and durable, the resin 
is first fused, then incorporated with heated oil, and 
afterward diluted with spirits of turpentine. A com- 
mon yarnish for maps, engravings, and similar objects, 
is made by dissolving mastic with a little Venice tur- 
pentine and camphor, in spirits of turpentine. Pounded 
glass is added to the pulverized material during the 
process of solution. The object is covered with a so- 
lution of isinglass before using this varnish, to prevent 
its absorption. Shellac, in alcohol, is employed to im- 
part to wood or other material a resinous coating, w T hich 
is afterward polished with rotten stone. Copal varnish 
is also similarly used. Shellac, dissolved in soda or pot- 
ash, is sometimes used to give body to paints, as a sub- 
stitute for part of the more expensive material. 

1093. Rosin Soap. — The resins possess an acid cha- 
racter, and like fats, form soap with the alkalies. Com- 
mon rosin is largely consumed, with fat and potash, in 
the manufacture of common brown soap. The greater 
hardness which it imparts depends on the formation of 
a certain portion of rosin soap in the mixture. 

1094. Sizing. — The soap which is formed on boiling 
rosin with strong potash is used in sizing paper. Being 
mixed with the material from which paper is to be 
made, a solution of alum is afterward added to the 
pulp, and a compound of rosin and alumina thus pro- 
duced in every portion of the mass. The pores of 
paper made from this material are thus completely 
filled, and the spreading of the ink prevented. A sur- 

1093, What is rosin soap ? 1064. How is rosin used in sizing paper ? 



536 ORGANIC CHEMISTRY. 

face sizing which is less effectual, is also given to paper 
by a solution of glue, applied after the paper is formed. 
When this is destroyed by erasure, its place may be 
supplied, and the spreading of ink prevented, by rub- 
bing powdered rosin upon the spot from which the siz- 
ing has been removed. 

1095. Sealing-wax. — Sealing-wax consists, princi- 
pally, of shellac. Venice turpentine is added to mate 
it more inflammable and fusible, and vermilion or lamp- 
black to color it. Ship pitch is resin changed and 
partially decomposed by heat. Shoemaker's wax is 
made by a similar process. 

1096. Rosnsr Oil and Gas. — Rosin is partially con- 
302 verted by dry distillation into an oil, which is 

largely used for adulterating other oils, and 
also for the purposes of illumination. A black 
pitch remains in the retort. The oil has the 
advantage of extreme cheapness, but owing to 
its large proportion of carbon, can only be 
burned in lamps furnished with tall chimneys. 
At a still higher temperature rosin is converted 
into gas, with a residue of carbon. 

1097. Gum Resins. — The dried juices of certain plants 
consist of mixtures of gum and resin. These mixtures 
are called gum resins. Water dissolves the gum, and 
holds the resin in suspension, thus forming what is called 
an emulsion. Alcohol, on the other hand, extracts the 



1095. What is the composition of sealing-wax ? 1096. What are the 
products of the dry distillation of rosin ? 1097. What is said of gum 
resins ? 




CAOUTCHOUC. 537 

resin from their mixtures. Assafoetida, gamboge and 
opium are a few of examples of gum resins. 

1098. Caoutchouc. Gum Elastic. — Caoutchouc is a 
hydrocarbon obtained from the milky juice of certain 
trees in Asia, Africa and South America. This con- 
stituent of the juice hardens on exposure to the air, 
while the remainder is removed by evaporation. By 
the addition of a little ammonia, the milk may be re- 
tained in its liquid condition. Caoutchouc is soluble 
in ether, spirits of turpentine, oil of coal tar, and many 
other hydrocarbons. Sulphuret of carbon, a volatile 
liquid obtained by passing sulphur vapors over ignited 
charcoal, is also a complete solvent of India-rubber and 
gutta percha. 

1099. Vulcanized Rubber. — Heated for a short time 
with sulphur, at 280°, or somewhat above this point, 
caoutchouc becomes remarkably changed in its nature, 
and is no longer stiffened by cold or softened by heat. 
It is then called vulcanized rubber, and constitutes the 
material out of which most India-rubber goods are now 
made. The hard rubber which is extensively employed 
for the manufacture of combs, knife-handles, pencil- 
cases, &c, is composed of pitch, India-rubber, sulphur, 
and magnesia. The mixture is softened at about 270°, 
then pressed into moulds to give it the required shape. 
It is afterward wrought like ivory. 

1100. Gutta Percha. — Gutta percha is identical in 

1098. Mention the sources and properties of caoutchouc. 1099. How 
is caoutchouc vulcanized? What are the properties of rulcanized " rub- 
ber ?" 1100. What is gutta percha? Mention some of its properties and 
uses. 



538 ORGANIC CHEMISTRY. 

composition with gum elastic, but possessed of quite 
different properties. Among them is its extreme tough- 
ness and comparatively slight elasticity. It is rendered 
soft and plastic by immersion in boiling water, and in 
this pasty condition may be moulded into any required 
shape. It can be vulcanized, like caoutchouc, and is 
then proof against elevation of temperature. It is em- 
ployed as a substitute for caoutchouc where great elas- 
ticity is not required. Both of the above substances 
approach more nearly in their composition to the essen- 
tial oils than to any other class of compounds. 

Protein Bodies — Putrefaction. 

1101. Vegetable Fibrin. — The glutinous mass which 
remains when dough is kneaded in water until all the 
starch is removed, is called gluten or vegetable fibrin. 
It differs from all the organic matter hitherto described, 
in containing nitrogen, with small quantities of sulphur 
and phosphorus. In the present state of our knowledge 
in respect to the protein bodies, we must abandon every 
formula designed to express their atomic constitution. 
They contain in a hundred parts : 55.16 carbon, 7.05 
hydrogen, 21.81 oxygen, 16.96 nitrogen, with \ to lper 
cent, sulphur and phosphorus in an unknown form. 
Gluten is a grey substance, and is the material which 
gives its cohesion to bread. 

1102. Vegetable Albumen and Casein. — Vegetable 

1101. State the composition and properties of vegetable fibrin. 1102. 
What is said of vegetable albumen and casein ? 



PROTEIN. 53'ci 

albumen is a similar substance, contained, in smaller 
quantity, in the juices of fruits and vegetables. It is 
coagulated by beat, like the white of egg, when the juices 
are boiled. Vegetable casein is another substance of 
very similar composition and properties, found princi- 
pally in the seeds of leguminous plants. It precipitates 
like the curd in sour milk, when a little acid is added 
to an aqueous extract of the seeds. These substances 
derive their names from their resemblance to animal 
fibrin, albumen, and casein. Vegetable casein is also 
called legumine. All of these substances were at one 
time supposed to be compounds of a single substance, 
called protein, itself free from both sulphur and phos- 
phorus. Later experimenters have not succeeded in 
isolating such a substance, and the theory is therefore 
abandoned. The name is retained in this work as a 
convenient designation of the class of substances here 
considered. 

1103. Occurrence. — One or more of these substances 
is present in greater or less quantity in all parts of 
plants. They are found accumulated with starch, in 
the fruit and seed. The seeds of cereals, such as wheat 
and rye, and those of leguminous plants, such as peas 
and beans, contain them in large proportion. 

1104. Characteristics. — If a bit of gluten be placed 
on the end of a wire and burned, a very different odor 
is produced from that of burning starch or wood. The 
smell approaches that of burning wool, and is a means 

1103. Where are the above substances found ? 1104. Mention a pecu- 
liarity of these nitrogenous compounds. 



540 ORGANIC CHEMISTRY. 

of distinguishing organic matter which, contains nitro- 
gen. If boiled with potassa, the sulphur of gluten is 
extracted, and the solution will blacken paper moist- 
ened with sugar of lead. This reaction furnishes 
another means of detecting these nitrogenous sub- 
stances. 

1105. Putref action. — A still more important distinc- 
tion of nitrogenous substances from those which con- 
tain no nitrogen, is their spontaneous putrefaction. 
Left to themselves, they are resolved, like blood and 
flesh, to which they are allied in composition, into a 
variety of other products. It is not strictly correct to 
say that this decomposition is spontaneous. The sub- 
stance must first have been exposed to the air. An 
oxidation or slow combustion is then commenced, which, 
although entirely imperceptible in its effects, and checked 
at once by exclusion of air, ensures the subsequent 
putrefaction. It burns out a small portion of carbon 
and hydrogen, and thus removes, as it were, the key- 
stone of the arch in every molecule. The atoms may 
then be supposed to fall together and re-arrange them- 
selves as is required by the known products of their 
decomposition. 

1106. Products of Putrefaction. — The re-arrange- 
ment which occurs in putrefaction, consists, essentially, 
in the combustion of the substance with oxygen, while 
the hydrogen divides itself between the nitrogen, phos- 
phorus and sulphur, forming ammonia, phosphuretted 

1105. Describe the process of putrefaction ? 1106. Mention some pro- 
ducts of putrefaction. 



FERMENTATION. 541 

and sulphuretted hydrogen. It is to these gases that 
the offensive smell which is given off in putrefaction is 
principally to be ascribed. 

Fermentation — Bread Making. 

1107. Fermentation. — Fermentation is a chemical 
action effected by certain substances and transferred to 
others, the primary substances being at the same time 
decomposed, though they do not communicate any of 
their elements to the new products. Any one of the 
nitrogenous substances above mentioned, while under- 
going the change which is called putrefaction, is capable 
by its mere presence, of acting as a ferment. A little 
putrefying gluten, for example, added to a solution of 
sugar, will convert it into alcohol and carbonic acid. 
Here again the key-stone of the molecule is removed, 
or rather in this case moved. The motion of the atoms 
of the putrefying substance would seem to be the cause. 
The effect is analogous to that of heat, through whose 
agency, also, complex organic bodies are resolved into 
others of simpler constitution. The process of fermen- 
tation is usually accompanied by the growth of a 
microscopic fungus, known as the yeast plant, which 
occurs in the change of sugar into alcohol or of vege- 
table juices into wine, beer or vinegar. 

1108. Yeast. — The first stage in the formation of 
yeast is the production of a microscopic vegetation, 

1107. What substances are capable of producing fermentation ? 1108. 
What is the first stage in the process ? 




542 ORGANIC CHEMISTRY. 

which consumes all the protein, converting it into the 
substance of a microscopic plant. Ordinary brewers' 
303 yeast is such a microscopic vegetation. 

Being produced, it passes immediately 
into the putrefaction above described, 
effecting, at the same time, the con- 
version of any sugar which may be 
present into alcohol and carbonic acid. 
By some, the growth of the microscopic plant itself, in- 
stead of its subsequent change, is supposed to be the 
cause of fermentation. 

1109. Production of Yeast. — Yeast has not only 
the power of converting sugar into alcohol, but it at 
the same time occasions the production of more yeast 
from dissolved protein. In the ordinary process of beer 
brewing, the newly formed yeast collects on the surface 
of the fermenting vats. It is thence removed, to serve 
as the excitant of a new fermentation, or to be employed 
in the production of bread, which is, chemically con- 
sidered, an analogous process. 

1110. Yeast for Culinary Purposes may be pro- 
duced by exposing a mixture of milk and flour for sev- 
eral hours to a temperature of about 90°. Sugar and 
salt added to a mixture of flour and water will have 
the same effect. The cook often fails to have the " yeast 
rise" from not keeping the mixture at the proper tem- 
perature. At a temperature below 70° the sugar is 
converted into lactic acid, and if it remains too long at 

1109. How is yeast produced ? 1110. How may yeast be prepared for 
culinary purposes ? 



FERMENTATION. 543 

this temperature, and is afterwards raised to the proper 
temperature for generating carbonic acid and alcohol, 
the mass is found too sour for making good bread; by 
raising the temperature at once to 90°, and keeping it 
at that point good yeast will be formed free from any 
mixture of lactic acid. Boiling water destroys the fer- 
menting properties of yeast, but unless boiled so long 
as to have its chemical nature entirely changed, it re- 
acquires a fermenting power on exposure to air. 

1111. Different kinds of Fermentation. — The pro- 
ducts of fermentation are different, according to tem- 
perature and other circumstances. Thus the same sugar 
which at 40° to 86°, with cheese used as a ferment, 
yields carbonic acid and alcohol, at a temperature of 
86° to 95° is converted into lactic acid. The latter, by 
the further action of the curd, with slight elevation of 
temperature, is converted into butyric and carbonic 
acids. By the same ferment, at a still higher tempera- 
ture, a portion of gum is produced with the lactic acid. 
These different processes of transformation have re- 
ceived, respectively, the names of the vinous, lactic, 
butyric, and viscous fermentations. The conversion of 
starch into sugar by diastase may be regarded as a 
species of fermentation. This substance is a slightly 
changed gluten. It is always produced in germination, 
and may be precipitated by alcohol in the form of white 
flakes from a concentrated infusion of malt. One part 
of it is sufficient to convert two thousand parts of starch 
into sugar. 

1111. Mention several kinds of fermentation. 



544 ORGANIC CHEMISTRY. 

1112. Flour. — Fine flour makes less nutritious bread 
than the coarser varieties, because it contains a smaller 
proportion of gluten. Gluten being tougher than the 
starch, is not reduced to so fine a powder and is par- 
tially separated in the process of bolting. All grains 
contain sugar in small proportion. Sugar is therefore 
one of the constituents of flour. 

1113. Deterioration of Flour. — When flour is kept 
for a considerable time it is very apt to absorb moisture 
and undergo a change by which the tenacity of the 
gluten is diminished. Flour from ground wheat is de- 
teriorated in the same manner. As a consequence, 
such flour does not make light bread. To make light 
bread of such flour alum is sometimes added, but this 
adulteration or addition to the flour is injurious to 
health. An analysis of bread from twenty-five bakeries 
in London showed the presence of alum in all, and a 
second examination some weeks afterward gave the 
same result. It was found, however, that in many cases 
the alum was not added by the bakers but by the mil- 
lers who prepared the flour. Liebig has shown that 
lime-water added to the dough in bread-making, whitens 
the bread, causes it to rise better, and that it is not in- 
jurious to health. 

1114. Bread. — The "raising of bread" is a process of 
fermentation. The yeast employed in the process con- 
verts a portion of the starch of the flour into sugar, and 

1112. W T hat is said of the nutritious properties of fine flour. 1113. 
How does flour deteriorate ? How is it restored so as to make nice 
bread ? 1114. What chemical principles are involved in making bread ? 



BREAD MAKING. 545 

subsequently into alcohol and carbonic acid. The sponge 
is made light and porous by the gas bubbles which be- 
come entangled within it. A large part of the alcohol 
produced in the process escapes into the oven, and thence 
into the exterior air. It may be condensed and con- 
verted into spirits by the proper apparatus. This has 
been successfully done in large bakeries in Europe, but 
the process has not been found to be of any considera- 
ble economical importance. In baking a small portion 
of starch is always converted into gum. By moisten- 
ing the baked loaf with water the gum is dissolved, and 
by a new heating, hardens into the shining surface 
which is often observed on bakers' bread. 

1115. Yeast Powders. — The gas which is needed to 
make bread light, may be produced by other means 
than the process of fermentation. If carbonate of soda, 
for example, is kneaded into the dough, and tartaric 
acid subsequently added in proper proportion, the 
weaker carbonic acid is expelled. A light sponge is 
produced by its escape, without the loss of the starch 
and sugar which are consumed in the process of fer- 
mentation. Soda and tartaric acid prepared for this 
purpose are known under the name of yeast poivders. 
Carbonate of ammoni#fceing entirely volatile by heat, 
may be employed alone for the same purpose. A por- 
tion of the salt probably remains in the bread, and is 
more or less injurious on account of its alkaline char- 
acter. 

1115. What materials are sometimes substituted for yeast ? 



546 ORGANIC CHEMISTRY. 

1116. Test for Yeast Powders. — The great objec- 
tion to the use of these powders in the preparation of 
bread, consists in their liability to contain soda or acid 
in undue proportion. Whether this is the case, may be 
ascertained by dissolving the powders in water and mix- 
ing the solutions. If the product is neutral to the taste 
and does not effervesce on the addition of either soda 
or acid, this fact will be evidence of their proper prep- 
aration. If otherwise, more or less injury is to be 
anticipated from their use. Excess of the alkalies 
especially interferes with the process of digestion, by 
neutralizing the acids which accomplish it. The use 
of soda and saleratus with sour milk is liable to the 
same objections. 

1117. Their Effect on Health. — It may well be 
questioned whether bread prepared by this process is 
ever as healthy as that made with yeast. For even the 
neutral tartrate, formed when the materials are used 
in proper proportion, will tend to neutralize certain 
stronger acids which are constituents of the gastric 
juice. It may thus interfere, in a measure, with the 
process of digestion. If pure muriatic acid were sub- 
stituted for the tartaric acid or cream of tartar, this 
objection would be removed. «*lhe product of its action 
on soda is common salt. 

1118. Aerated Bread. — By a recently invented meth- 
od, beautiful light bread is made without the use of any 

1116. What is the objection to the use of soda, &c., in bread? 1117. i 
What is said in addition, of their effect on the health ? 1118. How is 
aerated bread prepared ? 



BREAD BAKING. 547 

kind of yeast or yeast powders. The flour is placed in 
iron cylinders and deprived of air by a powerful air 
pump, and made into dough with, water holding in solu- 
tion a large amount of carbonic acid gas under high 
pressure. The operation of mixing and kneading the 
dough is performed by machinery in the closed cylinder. 
The dough is then run out into pans and quickly baked, 
the carbonic acid gas relieved from pressure and exposed 
to heat expands and raises the dough to a light spongy 
consistence, unsurpassed by the best bread raised with 
yeast. 

1119. Bread Baking. — When the prepared dough is 
exposed to the temperature of a hot oven (from 212° 
to 350°) it loses from ten to fifteen per cent, of the 
water which it previously contained, while another por- 
tion of the water enters into chemical combination with 
the flour, so that 100 pounds of flour make about 150 
pounds of bread. While the carbonic acid gas developed 
by fermentation, liberated by yeast powders or supplied 
in the aerated bread by carbonated water, gives the 
dough a spongy texture, the heat applied in baking 
solidifies the dough and renders the spongy texture per- 
manent. Baking converts a portion of the starch into 
gum, the gluten loses its tough qualities and unites with 
the starch. The heat of baking stops the fermentation 
and if sufficiently prolonged Mils the yeast plant. In 
imperfectly baked bread some of the yeast retains its 
vitality and when eaten sets up a fermentation very in- 
jurious to delicate stomachs. 

1119. What changes take place in baking bread ? 



548 ORGANIC CHEMISTRY. 

1120. New and Stale Bread. — The crust of newly 
baked bread is dry and crisp while the interior of the 
loaf is soft and moist, but after a short time both parts 
of the bread undergo a change, the brown crust attracts 
moisture and grows softer, while the interior becomes 
more dry and hard. This change is produced by new 
combinations between the water and the solid atoms of 
the bread. If a loaf of stale bread is exposed in a 
closely covered vessel for half an hour to a tempera- 
ture of 150°, it will again have the appearance of new 
bread with very little loss of weight since the first 
baking. 

Coloring Matters. 

1121. Indigo. — The vegetable dye-stuffs are extremely 
numerous. Indigo, madder and logwood are among 
the more important. Indigo is deposited from the 
colorless juice of certain plants by simple exposure to 
the air. It may be sublimed in purple crystals by rapid 
heating* By removing the oxygen absorbed in its pro- 
duction, the original colorless juice may be, as it were, 
reproduced from commercial indigo. This object is 
effected by the use of protosulphate of iron, which is 
converted into sulphate of the peroxide in the process. 
Caustic lime is at the same time added to dissolve the 
deoxidized indigo. The colorless solution is employed 
in dyeing ; cloth impregnated with it becomes blue on 

1120. How does stale bread differ from new ? 1121. What is said of 
indigo ? 



DYEING. 549 

exposure to the air. A solution of indigo in concen- 
trated sulphuric acid is also employed in dyeing. 

1122. Madder. — Madder is the ground root of the 
rubia tinctorium. This plant is cultivated extensively 
in India and Europe. It contains a red dye, produced 
by the action of the air or certain chemical agents upon 
the juices of the recent plant. This body is called ali- 
zarine and may be obtained in beautiful crystals. An 
infusion of the root in hot water contains a portion of 
this substance in solution. 

1123. Logwood. — This is a red wood, obtained from 
Spanish America and much employed in dyeing. Its 
coloring matter is called hematoxyline. By evaporating 
a decoction of the wood and re-dissolving in alcohol, 
this substance may be obtained, on a second evapora- 
tion, in the form of yellow crystals. 

Dyeing. 

1124. Dyeing. — Few dyes can be permanently im- 
parted to cloth without the intervention of some third 
substance, which shall, as it were, hold them together. 
Such a substance, with strong affinity for the coloring 
matter of the dye and also for the fiber of the cloth, is 
called a mordant. The fabric to be dyed being first 
impregnated with the mordant, is then introduced into 
the dyer's vat to receive its permanent color. 

1125. Mordants. — Alumina and oxide of iron are the 



1122. What is madder? 1123. What is logwood? 1124. Explain the 
theory of dyeing fast colors. 1125. What is said of mordants ? 



550 ORGANIC CHEMISTRY. 

principal mordants employed. They may be " fixed" 
in the cloth by immersion in the acetates of these ox- 
ides. A subsequent exposure for several days to the 
air is essential, in order that the acetic acid may in part 
be expelled. A portion of it, however, remains, so that 
the oxides are, strictly speaking, in the condition of basic 
acetates. After this exposure, and subsequent washing 
in hot water, the fabric may be immersed in the dye. 
An ounce of madder heated with a pint of water will 
be sufficient for an experiment. The fabric is to be 
boiled for an hour or more with the unstrained decoc- 
tion. 

1126. Preparation of the Mordant. — The solution 
of acetate of alumina is most conveniently prepared 
from alum, by the substitution of acetic for its sulphuric 
acid. This is accomplished by the addition of acetate 
of lead. Sulphate of lead is at the same time precipi- 
tated, and may be filtered off from the acetate which 
is formed. Three pounds of alum and two of sugar of 
lead to three gallons of water, are the proportions to 
be employed. This mordant produces a red color. 

1127. Yarious Colors by the same Dye. — By the 
use of different mordants, various colors may be pro- 
duced from the same dye. Substitute four pounds of 
green vitriol for the alum used in the previous case, and 
the madder gives a deep black. Add four ounces of 
arsenic with the green vitriol, and a mordant is pro- 
duced with which the dye will yield a beautiful purple. 

1126. How is the aluminous mordant prepared? 1127. How are various 
colors produced from one dye ? 



DYEING. 551 

In the latter case, the solution must be reduced to one- 
tenth of its original strength by the addition of water. 

1128. Dyeistg with Logwood. — By the employment 
of the last two mordants, mixed in equal proportions 
and diluted to half their strength by w^ater, a mordant 
for dyeing black with logwood is obtained. For dyeing 
purple with the same material, a tin mordant is used. 
It may be prepared by dissolving tin in muriatic acid 
with the gradual addition of nitric acid, then precipi- 
tating and re-dissolving with potassa. The cloth being 
impregnated with this mordant and thoroughly dried, 
is passed through dilute sulphuric acid, to remove the 
potassa and leave the oxide of tin. After subsequent 
drying and exposure to the air, the fabric is ready for 
the dye. 

1129. Mineral Dyes. — The dyes described in the 
following paragraphs, are distinguished from those be- 
fore mentioned by containing no organic matter. They 
consist of colored salts or oxides precipitated in the 
fiber of the cloth. Although these substances belong, 
strictly speaking, to inorganic chemistry, they are here 
introduced to complete the survey of the subject of 
dyeing and calico printing. 

1130. Prussian Blue. — A mineral blue may be pro- 
duced by impregnating cloth with the solution of ace- 
tate of iron, before described as a mordant, and then 
immersing it in an acidified solution of prussiate of 
potash. Prussian blue is thus precipitated in the cloth. 

1128. Describe briefly the process of dyeing with logwood ? 1129. 
What are mineral dves ? 1130. How is a mineral blue obtained ? 



552 ORGANIC CHEMISTRY.' 

This blue is found to be brightened bypassing it through 
a solution of sugar of lead. 

1131. Mineral Green. — A mineral green is pro- 
duced in the same manner by the employment of ses- 
quichloride of chromium, and subsequent immersion in 
potassa. The color consists of sesquioxide of chromium, 
precipitated from the chromium salt by the action of 
the alkali. The solution of the sesquioxide of chro- 
mium is prepared by the addition of sugar to a solution 
of bichromate of potassa in dilute sulphuric acid. A 
part of the oxygen of the chromic acid being abstracted 
by the organic matter, it is converted into an oxide, 
which remains in solution. 

1132. Chrome Yellow. — To produce a mineral yel- 
low, the cloth may be impregnated with acetate or 
nitrate of lead, then dried and passed through sulphate 
of soda, to fix the lead as sulphate in the cloth. On 
finally immersing it in bichromate of potassa, the cloth 
becomes dyed with yellow chromate of lead. The above 
process modified by printing instead of saturating with 
acetate of lead, gives yellow figures on a white ground. 

Calico Printing. 

1133. White Figures. — If it is desired to obtain a 
design in white, on goods dyed with either of the above 
madder colors, the design is printed with a paste of 
tartaric acid upon the colored cloth. On subsequently 



1131. How is a mineral green produced ? 1132. How is a mineral yel- 
low produced ? 1133. How is a white design on dyed goods produced ? 



HXY 



CALICO PRINTING. 553 

immersing the goods in a bath of chloride of lime, chlo- 
rine is evolved in the tissue, 

oOo 

and the color discharged only 
where the acid is printed. The 
white thus produced is of 
course in exact correspondence 
with the printed design. 

1134. Printed Yellow and Blue. — To produce yel- 
lows on madder red and purple grounds, before de- 
scribed, tartaric acid is printed with the nitrate of lead, 
and the cloth immersed in bleaching liquid. The color 
of the printed portions is discharged by the combined 
action of the acid and bleaching liquor ; the lead is at 
the same time fixed in the cloth as chloride of lead. 
On subsequent immersion in bichromate of potassa, the 
yellow figures of chromate of lead are produced as be- 
fore. For blues on the same colored grounds, a mix- 
ture of Prussian blue, dissolved in bichloride of tin, 
with tartaric acid, is printed on the cloth. The dis- 
charge of the ground color beneath the figure, is effected, 
as before, by chloride of lime. 

1135. Variegated Patterns. — All of the madder 
colors which have been mentioned, may be produced 
upon a single piece of white goods, by printing the dif- 
ferent figures of the pattern with different mordants. 
This is accomplished by passing the fabric between 
different sets of rollers, each of which is supplied with 
a paste of the proper mordant, and so engraved that it 

1134. How are yellow and blue designs obtained on dyed grounds ? 
1135. How are variegated patterns produced ? 



554 ORGANIC CHEMISTRY. 

yields the desired impression. On subsequently intro- 
ducing the goods into the madder bath, the various 
colors are developed. The whole piece is at the same 
time transiently colored ; but the dye may be readily 
removed from the unprinted portion by thorough wash- 
ing. A white ground for the colors is thus obtained. 

Relation of Plants to the Soil. 

AGRICULTURAL CHEMISTRY. 

1136. Mineral Constituents of Plants.— The mitu 
eral substances which plants obtain from the soil, are 
known by analysis of the ashes which they yield on 
combustion. They consist of acids and bases, which 
enter into the composition of all fertile soils. The 
bases are potassa, lime, magnesia and oxides of man- 
ganese and iron. These are found combined in the 
ashes with silicic, sulphuric and phosphoric acids, and 
are accompanied by small proportions of common 
salt. The carbonic acid which is found in certain ashes 
is produced in the combustion of the plant. The ashes 
of all cultivated plants contain the above substances ; 
but in different proportions according to the nature of 
the plant. The phosphates predominate in grains ; 
lime exists in large proportion in grasses; potash in 
edible roots; and silicia in straw. The approximate 
composition of the ash of different plants is given in a 
table in the Appendix. In estimating the relative pro- 

1136. What mineral substances do plants obtain from the soil ? 



COMPOSITION OF SOILS. 555 

portions of the different constituents which are ab- 
stracted from the soil by different crops, the quantity 
of the crop, as well as the composition of its ash, is of 
course to be brought into this account. 

1137. Composition of Soils. — Many of the above 
substances are contained in the soil in extremely small 
proportion. Soils are principally composed of vegeta- 
ble matter in a state of decay, with clay, sand and 
carbonate of lime. The vegetable matter consists of 
the remains of plants of previous years, and the clay, 
lime and sand are the product of the gradual crumbling 
and decomposition of the rocky crust of the earth. 

1138. Use of Vegetable Matter in Soils. — The 
wood, leaves and twigs of which vegetable matter is 
composed, furnish, in their gradual decay, the potash, 
silica, and other constituents of their own skeletons to 
form the framework of new plants. The organic mat- 
ter is at the same time converted into ammonia and 
carbonic acid; these constitute the gaseous food on 
which all vegetable life is sustained. 

1139. Addition of Vegetable and Animal Mat- 
ter. — The addition of more of this material to the soil, 
in the form of peat or muck from swamps, is of great 
advantage, because it increases the supply of the two 
important classes of materials which have been men- 
tioned. Animal matter of all kinds, whether decom- 
posed, as in stable manure and guano, or in its original 

1137. Of what are soils composed ? 1138. State the uses of vegetable 
matter in soils. 1139. What advantage is gained by the addition of 
vegetable and animal matter to soils ? 



556 ORGANIC CHEMISTRY. 

condition in the form of flesh, wool, and bones, is a 
still more valuable addition to the soil. The reason of 
its higher value, consists in the fact that while it yields 
most of the other substances which decaying vegetable 
matter supplies, it furnishes ammonia, which is the 
rarest and most expensive one, in much larger propor- 
tion. 

1140. Use of the Clay. — The clay in soils serves to 
retain the ammonia and certain other valuable mate- 
rials, which would, otherwise, be washed away by de- 
scending rains. It seizes not only upon that which 
comes from the decaying humus, but finds particles in 
the drops of every shower, which it stores safely away 
for the future use of the plant. It serves also to retain 
moisture in the soil, and to impart to it the tenacity by 
which the roots are enabled to gain a firm hold upon the 
earth. Soils which contain but a small proportion of 
clay are for these reasons improved by its addition. 

1141. Uses of the Sand. — Sand, where it exists in 
due proportion, gives the proper degree of porosity to 
the soil, and thus ensures the entrance of the air and 
fertilizing liquids, and the draining away of all excess 
of water. Access of air is important, because it brings 
with it fertilizing ammonia and carbonic acid, and by 
accelerating the decay of vegetable matter, produces 
more of these valuable substances. 

1142. Uses of the Lime. — The lime in soils, beside 
serving directly as building material for all forms of 

1140. What purpose does clay subserve in the soil ? 1141. What is the 
office of sand in soils ? 1142. What is the office of lime on the soil ? 



COMPOSITION OF SOILS. 557 

vegetation, is the key which unlocks other treasures of 
the soil and supplies them, also, to the growing plant. 
The building material which is furnished, as before ex- 
plained, by the decay of previous plants, is not suffi- 
cient. A portion of it never reaches the fields from 
which it was originally derived. Exported in the form 
of grain, or milk, or beef, it returns to the soil in some 
distant region or is poured into the rivers and the sea 
through the drains of populous cities. New supplies 
of potash and other material, are, therefore, demanded 
by the vegetation of every successive year. 

1143. A large part of the materials referred to are 
locked up in hard grains of granite or other silicates 
which are found in the soils. Being insoluble in water 
and the other solvents of the soil, they are inaccessible 
to the plant. Lime has the property of forcing itself 
into the rocky prison of every such insoluble grain, and 
setting part of its inmates at liberty. At the same time 
it opens the door to the action of other agencies which 
liberate the rest. They are then floated away in the 
water which penetrates the soil, and being in due season 
absorbed, are built into the substance of the plant. 

1144. Action of Lime on Mineral Matter ex- 
plained. — The action of lime, which has just been 
mentioned, is a simple consequence of its basic proper- 
ties. It takes possession of part of the silicic acid of 
of the alkaline silicate in the rocky grains. Their 
potassa and soda being now combined with this acid in 

1143. How does it accomplish the object? 1144. Give the chemical 
explanation of its action ? 



558 ORGANIC CHEMISTRY. 

small proportion, are soluble in the water which pene- 
trates the soil. 

1145. The water of the soil always contains a certain 
proportion of carbonic acid. This acid being itself 
material for vegetable nutrition, has also the property 
of dissolving those mineral substances which the plant 
needs for its support. By the joint action of carbonic 
acid and water, this transfer is constantly going on even 
without the aid of lime. But the latter substance very 
much acclerates the action, and thus adds greatly to the 
fertility of the soil. 

1146. Action of Lime on Organic Matter. — Lime 
has another important effect on soils, in hastening the 
decomposition of their organic matter, and thus, indi- 
rectly supplying in large quantity, valuable materials, 
before mentioned, which these are adapted to furnish. 
As this decomposition proceeds in the presence of lime, 
part of the nitrogen of the organic matter takes the 
form of ammonia, and part is converted into nitrates, 
as will be remembered from the Chapter on Salts. But 
the proportion of either is practically immaterial, as 
both are found to subserve a similar purpose in building 
up the plant. 

1147. All of the effects which have been mentioned, 
may be regarded as gradually produced in every soil 
which contains carbonate of lime as a constituent. 
"When it is deficient in quantity, they are, of course, 

1145. What other decomposing agent exists in the soils ? 1146. Men- 
tion another use of lime on the soil. 1147. How are the above men- 
tioned effects increased ? Mention another effect of lime. 



composts. 559 

increased by its addition in the form of chalk, marl, 
or limestone. These substances have also the effect of 
sweetening peaty and marshy soils, which are rendered 
sour from the presence of too large a proportion of 
vegetable matter, and thus rendering them fit for culti- 
vation. 

1148. Buened Lime. — Burned or caustic lime has all 
these effects in a much greater degree, and therefore its 
extensive use as a fertilizer of the soil. It should be 
used cautiously on soils which contain but a small pro- 
portion of vegetable matter, for fear that in the more 
rapid decomposition which it stimulates, it may entirely 
exhaust the soil of this material. If employed in such 
cases it should be with admixture of vegetable matter, 
that the loss which it occasions may be completely re- 
placed. 

1149. Effect of Ashes on Soils. — Potassa or soda 
applied in the caustic state, or as carbonates, have en- 
tirely analogous effects on the soil. They render the 
insoluble silicates soluble, by increasing in them the 
proportion of base, and also hasten the decay and con- 
version of vegetable matter. The admixture of lime 
or ashes with guano or decomposed manure is to be 
avoided, because of their effect to expel the ammonia 
which these substances contain. This may be prevented 
by previously incorporating the material with a large 
proportion of clay or vegetable mould, which shall 
serve as an absorbent of the liberated gas. 

1148. In what form has lime the greatest effect? 1149. What other 
substances act similarly ? What caution is to be observed in their use ? 



560 ORGANIC CHEMISTRY. 

1150. Composts. — Composts consist of vegetable and 
other matter, heaped together for fermentation and 
partial decay in order to prepare them for application 
to the soil. In such mixtures, all alkaline materials, 
including lime, have an effect similar to that which they 
produce upon the organic matter of the soil. 

1151. Guano. — Guano consists of the accumulated 
droppings of birds, and is principally obtained from 
certain rocky islands on the coast of South America. 
In these haunts of the heron, flamand, and other sea- 
fowl, it is accumulated, in some instances, to the depth 
of a hundred feet. The deposit is usually in smaller 
quantity, but amounts in the aggregate to millions of 
tons. The material was employed as a fertilizer by the 
natives of Peru and Chili, long before its introduction 
into England or the United States for the same purpose. 

1152. Different Varieties. — The quality of guano 
differs materially, according to the source from which 
it is derived. The ammoniacal salts, on which its 
agency as a fertilizer principally depends, being soluble 
in water, the product of moist climates is of compara- 
tively little value. The best is obtained from the coast 
of Peru, where rain seldom or never falls. The Afri- 
can, Patagonian and other varieties are much inferior. 

1153. Agricultural Yalue. — The agricultural value 
of guano lies principally in the ammonia and phosphate 
of lime which it is capable of yielding to plants. These 

1150. What is said of composts ? 1151. What is guano ? 1152. What 
is said of different varieties of guano ? 1153. On what does the agricul- 
tural value of guano depend ? 



ARTIFICIAL AMMONIA. 561 

constitute, in the best varieties, about one-third of the 
whole weight. Part of the ammonia is ready formed, 
and part is produced in the subsequent change which 
the nitrogenous matter of the guano experiences in the 
soil. The latter may be produced immediately by a 
chemical process, and its quantity accurately determined, 
In estimating the value of guano, it is customary to 
record the quantity of this potential ammonia, as if it 
were an existing constituent. 

1154. Artificial Ammonia. — The constituents of the 
ammonia which we purchase in the form of guano at 
so great expense and bring from distant regions of the 
earth, exist in unlimited quantities at our very doors. 
Four-fifths of the atmosphere is nitrogen gas, and the 
ocean is an exhaustless reservoir of hydrogen. But, 
strange to say, the chemist with all his skill, cannot, 
except by circuitous and expensive methods, effect their 
combination. The discovery of some cheap and ready 
means of accomplishing this object, would transform 
the face of the earth, by the unlimited quantity of fer- 
tilizing material which it would supply. This result 
may, perhaps, be reached by patient investigation. But 
no sudden triumph over nature need be anticipated. 
Improvements in agriculture will, as a general thing, 
be only realized by the earnest co-operation of scientific 
and practical men, in laborious and oft-repeated experi- 
ment. 

1155. Exhaustion of Soils. — When soils become ex- 

1154. What is said of the artificial production of ammonia ? 1155. 
What is said of the exhaustion of soils ? 



562 ORGANIC CHEMISTRY. 

hausted of those substances which form the mineral 
food of plants, the growth of vegetation ceases. It is 
never absolute, but consists in a great reduction of that 
portion of their material which is in a condition to be 
appropriated by the growing plant. Such soils are 
gradually restored by rest. A gradual decomposition 
of their insoluble material occurs by means of agencies 
which have before been mentioned, and the soil is thus 
restored to its original condition. These effects are 
very much hastened by plowing in such a growth as can 
be obtained. Eye, buckwheat and clover are among 
the plants best adapted to the purpose. Vegetable mat- 
ter is thus added to the soil, which, in its decay, hastens 
the decomposition of the soil its&Lf. 

1156. Deficiency of one or more Constituents. — 
The comparative exhaustion of some one or more of 
the constituents of the soil is a much more frequent 
occurrence. It is commonly the result of the cultiva- 
tion of the same crop during many successive seasons, 
and the consequent reduction of those materials which 
the particular plant requires in largest proportion. De- 
terioration of soils from this cause is repaired by an 
artificial supply of the failing ingredients. It is more 
wisely guarded against by such a rotation of crops as 
shall make different demands upon the soil in succes- 
sive years. 

1157. Maintenance of Fertility. — The effect of de- 
composing animal matters on the soil has been already 

1156. What is said of deficiencies in particular constituents ? 1157. 
What is said of the effect of decomposing animal matter in the soil ? 



MAINTENANCE OF FERTILITY. 583 

considered. They return the very material which was 
abstracted from the soil, with the addition of nitro- 
genous matter originally derived from the air by the 
growing plant. In an enlightened system of rural 
economy, the production of these materials in large 
quantity and their careful preservation, is therefore an 
object of paramount importance. The addition of 
gypsum or dilute sulphuric acid to fermenting manures, 
is of great advantage in retaining their ammonia in the 
form of sulphate and preventing its escape into the air. 
When additional ammonia is required, it is most cheaply 
obtained in the form of guano. The phosphates, whose 
quantity may be often increased with advantage, are 
best supplied in the form of " super-phosphate of lime." 
Other materials are less frequently required. For fur- 
ther information on the subject of the present section, 
the student is referred to works which treat especially 
of Agricultural Chemistry. 

1158. " Superphosphate of Lime." — The method em- 
ployed in the manufacture of " superphosphate of lime," 
has been already given in the Chapter on Salts. As in 
the case of guano, its agricultural value depends on 
actual or potential ammonia and phosphate of lime. 
In proportion as the phosphoric acid is in a soluble 
form, the value is much increased. 

1158. What is said of superphosphate of lime? 



CHAPTER III. 

ANIMAL CHEMISTRY. 

1159. Relations of Animal and Vegetable Life. 
— The life of animals is sustained by tlie consumption 
of material compounded and prepared by the plant, 
and converted into its own substance out of the mate- 
rials of the earth and air. This is virtually true 
even of the carnivorous species, for the animals on 
which they feed have derived their support from the 
vegetable world. When they yield their own flesh as 
food, it is only a changed vegetable matter which they 
thus supply. It thus appears that plants are pur- 
veyors for animals ; they take up inorganic matter and 
prepare it for the use of animals. All science shows 
that plants precede animals in the organic world. 
Animal compounds are in general more complex in 
their elementary composition and less permanent than 
substances of vegetable origin. Water and fat are 
found in the animal system and they contain only two 
or three elements ; but other animal compounds are 
rich in nitrogen, sulphur, and phosphorus. 



1159. How is the life of animals sustained ? 



ANIMAL SOLIDS. 565 



Animal Solids — Bones, Flesh, etc. 

1160. Boxes. — Bones consist of earthy matter and a 
cartilaginous material commonly known as gelatine. 
The bone earth or mineral matter is principally phos- 
phate of lime, and forms in mammiferous animals about 
two-thirds of the whole weight. The remaining third 
is cartilage. Either of these constituents may be re- 
moved from the bone without effecting its shape. By 
removal of the cartilage, a brittle, earthy framework 
remains. By removal of the earthy material a per- 
fectly flexible mass is obtained, of a form entirely 
similar to that of the original bone. The first change 
may be effected by long digestion in dilute muriatic 
acid, and the latter by fire. If in the second process 
the cartilaginous matter is not entirely consumed, bone 
black or animal charcoal is produced, the uses of which 
have been already described. 

1161. Flesh. — Lean flesh or animal muscle is com- 
posed of fibrine, penetrated by a liquid which forms 
four-fifths of the whole, and is called flesh fluid, or juice 
of the flesh. It contains a peculiar organic acid pos- 
sessing the flavor of broth, crystalline substances called 
creatine and creatinine, and certain salts. Being ex- 
tracted by cold water and then heated, it forms a nour- 
ishing and highly flavored soup. Hot water coagulates 
its albumen and prevents its escape from the flesh. 

1160. What is the composition of hone ? How is it shown ? 1161. 
Of what does flesh consist ? 



566 ORGANIC CHEMISTRY. 

Gradual heating is on this ground to be recommended 
in the preparation of soups, while sudden exposure to a 
high temperature, both in boiling and roasting, yield 
more nutritious and highly flavored meats. The salts 
of potash prevail in the flesh fluid, while those of soda 
are more abundant in the blood. Unlike the blood, 
this fluid is acid in its reaction. 

1162. Structure of Muscle. — Lean meat or nrtjjlfte 
consists of fibers enclosed in delicate membranous 
sheaths ; these fibers are united into larger bundles 
which act together, constituting a muscle ; each muscle 
is enveloped in a fibrous sheath, and in general con- 
tiguous muscles are separated by more or less fatty 
tissue which allows them to glide easily upon each 
other. Single muscular fibers when highly magnified 
are seen to possess transverse striations, they may also 
be torn apart and separated into numerous fibrillse or 
306 smaller threads, as shown in 

figure 306, each fibrilla ap- 
pearing somewhat like a 
string of beads. Each mus- 
cular fiber or bundle of 
fibrillae is supplied with 
blood vessels and nerves too 
delicate to be shown in the 
figure, which although magnified 350 diameters, repre- 
sents only a portion of a muscular fiber. Muscles 
possess the power of contracting and thus move the 
body. Some muscles not under the control of the will 

1162. Describe the minute structure of muscles. 




ANIMAL SOLIDS. 567 

are also destitute of striations. They act more slowly 
than voluntary muscles. Such muscles are found in 
the blood-vessels and intestines. 

1163. Skin, Tendons, Ligaments. — The cartilaginous 
material above mentioned as a constituent of bones, is 
transformed by boiling water, without change of com- 
position, into gelatine or glue. The skin, cellular 
membrane, tendons and ligaments of the body undergo 
the same change, and yield the same product. Gela- 
tine may even be prepared from refuse leather, by first 
extracting the tannin, and thus reducing it to the con- 
dition of the original hide. The tannin obtained in 
the process may also be employed for tanning new 
hides. Hoofs, hair, horn, and feathers, although very 
similar substances, are not thus affected by boiling. 

1164. Gelatine. — Gelatine is soluble in water, and 
yields a stiff jelly on cooling from a hot solution. On 
this property is based its use in the preparation of 
jellies for the table. The commercial article em- 
ployed for this purpose and ordinary glue are essentially 
the same. 

1165. The substance known as isinglass, is the dried 
air bladder of a species of sturgeon, and forms in its 
natural condition a soluble gelatine. Gelatine contains 
the four principal organic elements ; nitrogen and oxy- 
gen being in somewhat larger proportion than in the 
protein bodies. Hoofs, hair, and other substances above 
mentioned, contain sulphur in addition. Gelatine is 

1163. What is said of tendons and ligaments ? 1164. What is gelatine ? 
1165. Give the composition and properties of gelatine? 



568 ORGANIC CHEMISTRY. 

susceptible, like protein bodies, of putrefaction, and 
also of exciting fermentation. As starch is changed 
into sugar by the action of dilute sulphuric acid, so by 
the action of oil of vitriol, gelatine may be converted 
into a sweet crystalline substance called glycocoll or 
sugar of gelatine. 

1166. Hides, Tanning. — A solution of gelatine forms 
with tannin or tannic acid a tenacious insoluble pre- 
cipitate. The tanning of leather depends on the forma- 
tion of this insoluble compound in the hides which are 

submitted to the process. They are im- 
mersed for this purpose in an infusion of 
oak and hemlock bark, until the combina- 
tion has taken place throughout the whole 
thickness. They are thus secured against 
putrefaction and converted into firm, elastic 
leather. Hides may also be preserved by soaking them 
in alum and afterward in oil. Soft chamois leather is 
prepared by working the skin with fat alone. 

Fats. 

1167. Composition. — "We have already seen that there 
are both acids and bases of purely organic origin, and 
that these may combine like the similar compounds of 
inorganic chemistry, to form salts. The animal fats 
and oils are mixtures of such compounds in different 
proportions. The principal of these organic salts are 

1166. What chemical combination occurs in tanning ? 1167. What is 
said of the constitution of fats ? 




FATS. 569 

stearine, margarine, and oleine. Stearine is solid, 
oleine fluid and margarine occupies a middle position 
between the two. The difference of consistence in 
butter, lard, and tallow, is owing to varied proportions 
of these three substances which enter into their compo- 
sition. Beside the fats contained in other parts of the 
body, the brain and nerves of animals contain, with 
albumen and water, certain peculiar acids and fats. 

1168. Separation of Fats in Oil. — The' stearine and 
oleine of whale oil separate spontaneously in cold 
weather. The cold which is sufficient to harden the 
former, leaves the latter in a fluid condition. This 
effect is often observed in lamps during winter weather. 
The case is quite analogous to the separation of cider 
into alcohol and water by freezing. The water con- 
geals, and leaves the alcohol fluid. Both separations 
are imperfect. As the alcohol produced by the above 
process is diluted to a large extent with water, so 
the oleine retains a considerable portion of stearine in 
solution. 

1169. Separation of Fats in Tallow and Laed. — 
Stearine is obtained from lard and tallow on a similar 
principle. It hardens on partially cooling the melted 
fat, forming a mass from which the fluid oleine may 
be separated by pressure. Stearine thus obtained is 
used in the manufacture of candles, while the oleine 
forms lard or tallow oil. The former has, of late years, 
given place to stearic acid, procured from the same 

1168. How may the constituents of oil be separated ? 1169. How may 
the different fats of tallow be separated ? 



570 ORGANIC CHEMISTRY. 

sources, by means to be hereafter described. Marga- 
rine may be separated from butter by similar beating 
and slow cooling. It is regarded by some chemists as 
a simple mixture of stearine and oleine and not a dis- 
tinct substance. 

1170. Glycerine. — Glycerine is the base of all the 
fatty salts which have been mentioned. It is a viscid, 
sweetish liquid containing the same elements as grape 
sugar, and in nearly the same proportion. On remov- 
ing the stearic, and oleic acids from melted stearine or 
oleine, it remains in the liquid form. This removal 
may be effected by lime. The white lime compound 
floats upon the water which is used in the process, 
while glycerine is dissolved. 

1171. Stearic Acid. — The compound formed by lime, 
as described in the last paragraph, if tallow has been 
used in the process, is a mixture of oleate and stearate 
of lime. From these, stearic and oleic acids are 
liberated by the agency of diluted oil of vitriol. The 
material floats on the dilute acid, gradually losing lime 
and becoming transparent by its action. Sulphate of 
lime or gypsum is formed at the same time and sinks 
to the bottom of the vessel. The stearic and oleic 
acids are drawn off while yet warm, and run into cubi- 
cal moulds. The latter is subsequently removed from 
the mixture by gentle heat and pressure. The remain- 
ing stearic acid is then remelted and allowed to cool 
slowly. It is thus obtained in a brilliant white mass, 

1170. What is glycerine ? How is it made ? 1171. How is stearic acid 
made ? 



soaps. 571 

of crystalline texture, with the luster of mother of 
pearl. This material is principally employed in the 
manufacture of candles. Its superiority to stearine for 
this purpose, consists in the fact that it is less softened 
by heat. The two substances differ in their melting 
point about ten degrees. 

1172. Soaps. — Soaps are compounds of stearic and 
oleic acids with caustic potash or soda.* Theyare pro- 
duced by boiling fats with either of the alkalies, until 
the mixture becomes nearly or quite transparent. The 
glycerine which is expelled from the fats in the process, 
remains mixed with the soap which is produced. Pot- 
ash soaps are soft. Soda soaps may be converted into 
a floating coagulum, and separated from the water used 
in their preparation by means of common salt. This 
method is employed to give them their hardness. The 
action depends on the insolubility of the soap in salt 
water. Salt added to potash soap seems to have the 
same effect. But its action in this case is due to a 
double decomposition, in which a floating soda soap is 
formed, chloride of potassium remaining in solution. 
Soaps may also be made without the use of water, by 
combining oil or fat with melted potash. 

Hard soap is made with soda, the soda being able to 
absorb more than its own weight of water without be- 
coming fluid. Potash soap is soft because of its great 

1172. How are potash and soda soaps prepared ? 



* In the ordinary preparation for soap making, the lye is made to pass through 
lime in the leach tub, that its carbonic acid may be partially removed. 



572 ORGANIC CHEMISTRY. 

affinity for water; potash being deliquescent. The 
best hard soap usually contains 25 per cent, of water. 
Eosin is mixed with fat in the manufacture of soap to 
increase its hardness. § 1093. Silicate of soda is also 
largely employed in the manufacture of washing soap. 
A suitable proportion of this compound is said to im- 
prove the quality of the soap at the same time that it 
diminishes the cost of production. § 881. 

1173. Liniments, etc. — Soaps are soluble in alcohol, 
forming the tinctiore of soap which is used for bruises. 
With the addition of camphor, this tincture forms opo- 
deldoc, a compound more efficient than the simple tinc- 
ture of soaps. Transparency is imparted to soap by 
the evaporation of an alcoholic solution of the well 
dried material. Liniments are soaps prepared from 
ammonia and oil by the simple agitation of the materials. 

1174. Properties of Soaps. — Soaps which are pre- 
pared, as above seen, from oils and fats, have the prop- 
erty of dissolving more of the same material. On 
this property their cleansing effect principally depends. 
"When they are dissolved, a portion of the alkali be- 
comes free by the substitution of water as base. This 
free alkali adds to the cleansing effect, by its own 
affinity for the oils and other organic matter. Alkalies 
alone are not equally effectual ; they tend to shrink the 
fiber of cloth, and thus protect it against a perfect puri- 
fication. The strength of the tissue is at the same 
time gradually impaired. 

1173. How are transparent soaps and liniments prepared? 1174. Ex* 
plain the cleansing action of soap. 



ANIMAL FLUIDS. 573 

Soap is freely soluble in pure water, but in salt water 
it is insoluble ; soap made from the oil extracted from 
the cocoanut is an exception to this rule, as it dissolves 
freely in salt water, and is hence much used as marine 
soap. Hard water, or water containing salts of hme or 
magnesia decompose soap, forming a slimy scum, hence 
such water is unfit for washing unless a portion of free 
alkali or an additional quantity of soap is added.* 



Animal Fluids— Blood, Milk, Etc. 

1175. The Blood is the most important and well 
known fluid of the animal system. In man and the 
higher animals the blood is red, being of a bright scar- 
let hue when taken from the arteries and of a some- 
what darker hue when drawn from the veins. Healthy 
blood is about five per cent, heavier than water, and is 
always alkaline to test paper. It is unctuous to the 
touch and has a peculiar odor which differs in different 
animals. When first removed from the body the blood 
appears to be a uniform red liquid, but when viewed 
with a good microscope it is found to consist of two 
parts, a nearly colorless fluid called the blood plasma 
or the nutrient fluid, and an immense number of cir- 



1175. What is the appearance of blood, and what solid bodies does it 
contain ? 

* The hardness of water may be easily tested by adding a few drops of tincture 
of soap. If the water remains clear it is perfectly soft ; if it becomes cloudy, it 
may be regarded as hard— the degree of hardness being proportioned to the degree 
of cloudiness caused by adding the tincture of soap. 



574 



ORGANIC CHEMISTRY. 



cular or elliptical disk-shaped bodies or corpuscles 
floating in the fluid of the blood. In man and the 
mammalia generally, these corpuscles are circular, as 
shown in figure 308. But in birds, fishes, and reptiles, 



308 





they appear generally, as shown in figure 309, of an 
elliptical form with a central nucleus. Besides the 
colored corpuscles some colorless bodies are seen, as at 
a, a, figure 309, which have a granulated appearance, 
they are called white corpuscles. In some cases the blood 
disks adhere together like rolls of coin, as in some parts 
of figure 308, but they gradually become disunited and 
scattered. 

1176. Composition of the Blood. — If fresh blood is 
beaten with a branched stick, it is separated into a 
slightly alkaline liquid called the serum, a fibrous 
material called jibrine, and red globules, mentioned 
above, which sink, after a time, to the bottom of the 
vessel. The fibrine adheres in threads to the stick 
with which the operation is performed. It is analogous 
in composition and properties to the vegetable gluten 



1176. Give the composition of blood. 



BLOOD, MILK, ETC. 575 

from which it is formed. The serum contains albumen, 
and resembles the white of egg. The globules are also 
principally albumen, with a small proportion of a red 
coloring matter called hematosine. Albumen and 
fibrine both contain phosphate of lime or bone earth. 
The serum contains, also, certain salts, and a small pro- 
portion of fat. All of these substances together form 
but about one-fifth of the blood ; the remaining four- 
fifths are water. When blood is left to stand, after 
being drawn from the body, the fibrine coagulates 
spontaneously, entangling and taking with it the red 
globules, and thus separating them from the serum. 

1177. Milk. — Milk is analogous to blood in composi- 
tion, as is implied in the office which it fulfills in the 
nutriment of the young animal. But casein takes the 
place of the fibrin of the blood, and fat is also found in 
milk in much larger proportion. This fluid also contains 
sugar, which is peculiar in its character and has there- 
fore received the name of sugar of milk. The opacity 
and whiteness of milk are due 310 

to minute globules of fat which qoq 0%^ ' 

appear to be surrounded with a $ty*\ Ql <n>® 
thin covering of insoluble matter, 
differing in its properties from 
fat, and probably composed of a 
modification of protein. Figure 
310 shows the appearance of milk globules magnified 
400 diameters. The size of milk globules varies from a 
mere point to ttqV °^ an ^ nc -' 1 ^ n diameter, the average 

1177. What is the composition of milk ? 



c 




576 ORGANIC CHEMISTRY. 

being 7 oV?r of an inch. Butter is produced by the 
coalescence of the small particles of oil which are 
suspended in milk, and partially separated in the cream. 
The operation of churning breaks the envelope which 
surrounds the fat and brings the fat or butter into large 
masses. Chemically considered, butter is a mixture of 
oleine and margarine. On partially cooling melted 
butter, the latter collects at the bottom of the liquid 
oleine, which forms the other constituent; a portion 
at the same time remains in solution. Beside the 
above substance, butter contains phosphates and other 
salts, with certain neutral fats from which it derives its 
flavor. 

If butter remains exposed for some time to the air, 
some volatile fat acids are formed having a disagreeable 
smell and taste ; these cause the rancidity in butter. 

If butter that has been rancid is boiled several times 
with double its quantity of water, these acids will be 
removed from it, and the butter, on cooling, will have 
regained its original flavor. Butter thus restored does 
not regain its original appearance, but it may be used 
in cooking. 

1178. Cheese. — On exposure to the air for a consider- 
able time, the sugar contained in milk is partially con- 
verted into lactic acid, and the casein is precipitated. 
One reason of this precipitation is to be found in the 
neutralization of the free alkali of the milk. The 
casein having thus lost its solvent assumes the solid 
form. The coagulation of milk may also be effected 

1178. Why is the curd separated by exposure to the air? 



SALIVA. 577 

by rennet, which consists of an infusion of the lining 
membrance of the stomach of the calf. Its mode of 
action is not well understood. In making cheese the 
process is so conducted as to retain the fat or butter 
mingled with the solidified casein. This imparts to 
cheese its richness and excellence. 

1179. Solid Milk. — Milk may be brought into the 
solid form by careful evaporation with a moderate heat. 
It must be constantly stirred during the process. A 
machine has been recently patented which secures all 
of these objects. "With the addition of a little soda 
and gum, milk may be thus kept sweet in the solid 
condition for many months. The addition of water 
is all that is necessary to restore it to its original 
form. 

1180. The Fluids Concerned in Digestion are the 
saliva secreted by the glands about the mouth, the 
gastric juice secreted by the stomach; the bile secreted 
by the liver and modified by the secretions of the gall 
bladder ; the pancreatic fluid secreted by the pancreas. 
These fluids will be considered in connection with the 
process of digestion. 

1181. The Saliva is a fluid secreted by the parotid 
and other glands shown at 1, 2, 3, figure 313, the ducts 
of which empty themselves into the cavity of the 
mouth. This fluid lubricates the mouth, moistens the 
food and facilitates the act of deglutition. In addition 
to mucus the saliva contains a peculiar organic prinei- 

1179. How is solid milk prepared ? 1180. What fluids are concerned 
in digestion ? 1181. What are the properties of saliva ? 



578 



ORGANIC CHEMISTRY. 



pie termed ptyalin, resembling albuminate of soda, 
which is very prone to putrefaction. Ptyalin has the 
property of converting starch, even in the granular 
form into dextrin and into sugar. The flow of saliva 
into the mouth is greatly increased by the movements 
of the jaws in mastication. Hence food that is 
thoroughly masticated is more readily digested than 
that which is swallowed without sufficient mastication. 
1182. The Gastric Juice, as its name implies, is a 
fluid poured out from the lining membrane of the 
stomach. This important secretion is the principal 
agent in effecting the digestion of the 
albuminoid portions of the food, but 
it exerts scarcely any action upon 
starchy and fatty constituents. Fig- 
ure 311 gives a magnified view of the 
honeycomb appearance of the lining 
membrane of the stomach, in which 
are seen the orifices of the glands 
which pour out the gastric juice. 
Figure 312 shows longitudinal sec- 
tions of the gastric glands from the 
stomach of a dog 5 c, d, being their 
orifices, and <?,/*, the closed portions 
imbedded in the walls of the stomach. 
These follicles or glands are covered 
with a delicate network of blood- 
vessels terminating in veins which 
surround their outlets upon the surface of the mem- 




1182. Where is the gastric juice formed ? 



GASTRIC JUICE. 579 

branes, while nerves without number pervade the entire 
structure. While the stomach contains no food, and is 
inactive, no gastric fluid is secreted, and mucus which is 
either neutral or slightly alkaline covers its surface. 
But as soon as food or other foreign substances enter 
the stomach, the mucus membrane, previously quite 
pale, becomes slightly turgid and reddened with the 
influx of a larger quantity of blood, the gastric glands 
commence secreting actively, and an acid fluid is 
poured out in minute drops which gradually run to- 
gether and flow down the walls of the stomach, or 
soak into the substances introduced. 

1183. Properties or Gastric Juice. — When separated 
from mucus by filtration it is a colorless limpid liquid, 
having a peculiar odor, and an acid reaction from the 
presence of lactic and hydrochloric acids. It some- 
times contains phosphoric acid combined with lime. 
It contains also common salt, chlorides of calcium and 
magnesium, and some traces of iron. 

The gastric juice contains also a small quantity of a 
peculiar nitrogenous organic compound termed pepsin^ 
upon which, in conjunction with the free acid, its re- 
markable solvent and digestive powers depend. Pepsin 
is an albuminoid body, soluble in water, but insoluble 
in alcohol. Its aqueous solutions are precipitated by 
corrosive sublimate, by salts of lead, and by solutions 
of tannic acid. "When boiled it loses its peculiar power 
of effecting digestion. Fibrin or coagulated albumen 
plunged into gastric juice, at the temperature of the 

1183. What are the properties of gastric juice ? 



580 ORGANIC CHEMISTRY. 

body, swells up and becomes gradually disintegrated 
and dissolved. This property of dissolving fibrin and 
analogous substances lias been verified by experiments 
on animals ; and in one remarkable instance in a 
human being, in whose stomach there was a fistulous 
opening. 

Medicinal pepsin consists of the dried mucus scraped 
from the interior of the stomach of animals (the sheep 
and the pig). It is sometimes incorporated with starch. 
Soluble pepsin consists of this substance dissolved in a 
solution of chloride of sodium. It is supposed to sup- 
ply additional digestive power to those whose stomachs 
are unable to secrete a sufficient quantity of pepsin. 

1184. The Pancreatic Fluid is secreted by the pan-, 
creas. It resembles saliva in some respects. It has an 
alkaline reaction and putrefies rapidly. It possesses in 
an eminent degree the power of changing starch into 
sugar, and it appears to assist in an important man- 
ner in the digestion of starchy food, which is not ren^ 
dered soluble by the action of the gastric juice. In 
this respect the pancreatic fluid resembles saliva, but 
its characteristic property is to assimilate oily matters. 
It forms an emulsion with all oils and fats when mixed 
with these substances at the temperature of the body. 
Chemically, this appears to be a process of saponifica- 
tion, by which glycerine is produced and the fatty acids 
are set free. 

1185. The Bile is a viscous yellow or greenish fluid 
of a strong bitter taste. The quantity of bile daily 

1184. What is said of pancreatic fluid ? 1185 What is said of the bile ? 



THE BILE. 581 

secreted by the liver has been estimated at seventeen or 
twenty-four ounces, but the amount varies under a great 
variety of circumstances. The bile secreted by the liver 
differs much in appearance from that which is taken 
from the gall bladder where it accumulates as in a 
reservoir. The gall bladder is an organ largely sup- 
plied with very large blood-vessels, from which it 
secretes mucus, and perhaps other principles, which, 
added to the bile as it comes from the liver, gives to 
cystic bile its peculiar character. - 

1186. Composition of Bile. — Bile has a specific 
gravity of 1.024, and possesses a slightly alkaline reac- 
tion. It mixes with water in all proportions, giving it 
a yellow color and a viscid frothy consistence. 100 
parts of ox bile contain 9.2 parts of solid matter. The 
bile essentially consists of salts of two pecucliar organic 
acids, in which soda is the base, namely, the cholate 
and choleate of soda, of cholesterine and fat as well as 
mucus and coloring matter. The cholic and choleic 
acids are of the nature of resinous and fatty acids, and 
were formerly included under the name hilin or resin 
of the bile. Their salts give to the bile a saponaceous 
character. Hence ox gall is a powerful detergent, and 
is much used as such in manufactures and the arts. 

1186. Of what is the bile composed ? 



* Bile for analysis is taken from the gall bladder so that we do not know the 
chemical difference between hepatic bile and cystic bile. But bile as found in the 
liver has a sweetish taste, while bile from the gall bladder is very bitter. Some ani- 
mals, as the horse, have no gall bladder, from which it is inferred that the gall blad- 
der exercises no very important influence upon the bile which is collected into this 
organ from the liver. 



582 



ORGANIC CHEMISTRY. 



VIEW OF THE NUTKITIVE SYSTEM OF A DOG. 
313. 




DIGESTION. 583 

Cholesterine when obtained in a pure state consists of 
colorless scales, lighter than water, which melt at 293°. 
Briefly, we may say, that analysis of 1000 parts of bile 
gives water 908 parts, mineral matter containing much 
soda 12 parts, cholic and choleic acids, with mucus and 
fat, 80 parts. No albumen is found in the bile, but its 
organic constituents contain a small percentage of 
nitrogen. It also contains a notable quantity of sulphur. 
Sugar is not an ingredient in normal bile, but it is re- 
markable that this substance is rapidly formed after 
death from one of the constituents of the liver itself. 
The action of the bile in digestion in the living body 
does not admit of any satisfactory chemical explana- 
tion. It is supposed to assist in preparing starch and 
oil for absorption and for being carried into the blood. 

1187. Progress of Digestion. — The food received 
into the mouth is broken up and comminuted by the 
teeth, and at the same time it is moistened and lubri- 
cated by the saliva which acts upon the starchy por- 
tions to change them into sugar. The muscles of 

1187. Describe tlie general course of digestion ? 



In figure 313 is shown the arrangement of the organs of a dog, which are con- 
cerned in nutrition. A is the trachea ; B. lungs ; (?, vena cava ; Z>, liver ; 
i?, stomach ; F, spleen; £, receptacle of the chyle; i7^ pancreas; 7, duodenum; 
J, entrance of biliary and hepatic ducts ; E, jejunum ; X, ileum ; P, kidneys 
with supra-renal capsules above. The ureters or tubes "which carry away the 
water discharged by the kidneys are seen on each side of 17, and they may be 
traced back to the kidneys. S t the thoracic duct through which the chyle passes 
to join the blood. 1, 2, 3, the parotid and other salivary glands ; 4, jugular and 
subclavian veins ; 5, situation of thymus and thyroid glands; 6, entrance of thoracic 
duct into the left subclavian vein near the jugular; 7, left auricle of the heart; 
8, right auricle ; 9, left ventricle ; 10, right ventricle ; 12, vena portae which conveys 
blood from the intestines to the liver ; 13, mesenteric glands ; 14, lymphatic vessels ; 
15, lacteals ; 16, branches of the portal vein ; 17, ureters. 



584 ORGANIC CHEMISTRY. 

deglutition then act and carry the masticated food into 
the stomach, where it remains for a considerable time 
and is moved about by the muscular contractions of the 
stomach until it is thoroughly mingled with the gastric 
juice and a considerable portion is dissolved, forming a 
semi-fluid mass called chyme. The delicate blood ves- 
sels extended upon the lining membrane of the stomach 
absorb some portions of the liquid food, but the greater 
portion passes through a valvular opening into the in- 
testines, where it meets with the pancreatic liquid and 
the bile, by the action of which it is still further 
digested and dissolved. As it moves onward through 
the intestines the nutrient portions in a fluid state are 
taken up by peculiar vessels called lacteals, and carried 
into the common receptacle of the chyle (receptaculum 
chyli). From this receptacle the chyle is carried by 
the thoracic duct to the left subclavian vein, "which 
empties into the right auricle of the heart. The 
nutrient portions of the food are thus carried in a fluid 
condition, to the heart, w^here they mingle with the 
blood and join the general circulation. The organs 
here referred to are shown in figure 313. That part 
of the food which is not rendered soluble by digestion, 
and is hence unfit for assimilation, is left unabsorbed 
by the lacteals and passes off through the intestines 
in the form of excrementitious matter. 

1188. Preparation of Food. — Most of the food used 
by man is prepared by cooking. By boiling, vegetable 

1188. How is food changed by boiling ? Why do domestic animals 
fatten more i >pidly on cooked food than on raw ? 



PREPARATION OF FOOD. 585 

acids, sugar, gum, and vegetable albumen are partially 
removed ; solid tissues are softened so that the y are more 
readily broken up by mastication, and rendered more 
permeable by the saliva and gastric juice. Cells con- 
taining starch grains are broken by steam formed 
within. Starch grains themselves, shown in Figure 
284, page 489, may be broken up by pressure so as to 
assume the appearance shown in Figure 314, but boiling 
causes them to swell up, and separates the layers as 

315 





shown in Figure 315. By further boiling, the starch 
asssumes a gelatinous consistence, and gradually changes 
first into gum and then into sugar. Hence boiling 
aids mastication and causes a commencement of those 
chemical changes which digestion is intended to com- 
plete. Much of the food that is taken raw passes 
through the system unchanged, and of course is use- 
less for the purpose of nutrition. Nutrition depends 
not merely upon the amount of food taken into the 
stomach but upon the amount digested and absorbed. 
It is well known that domestic animals fatten more 
readily on vegetables or grain that have been boiled than 
if they are fed upon the same food uncooked. 

Cooking meat is designed principally to soften the 



5S6 ORGANIC CHEMISTRY. 

fibrous tissues of which it is composed, and to melt the 
fat and to cause it to flow out from the cells in which 
it is contained. The different effects of gradual and 
rapid heating, either in water or in the oven have been 
already mentioned in Section 1161. 

1189. Liebig's Extract of Meat is prepared by put- 
ting a pound of lean meat chopped fine into a pint of 
cold water, to which is added four drops of muriatic 
acid and a half a teaspoonful of salt. After standing 
for an hour the liquid is strained through fine muslin, 
when it is ready for use. The shreds of meat which re- 
main are nearly white and almost tasteless, while the 
liquid contains most of the nutritious principles of the 
meat in a fluid condition, especially adapted to the use 
of invalids. This juice of meat is given cold without 
cooking, as boiling would coagulate the albumen and 
fibrin, and render it less digestible. 

1190. The Effect of Salt when rubbed upon raw 
fresh meat is to draw out the juices of the meat so that 
its fibers contract and a brine is formed without the 
addition of any other liquid. Meat thus deprived of 
its juices is less nutritious than fresh meat, and men 
fed upon salt meat alone, unless supplied with albumen 
and fibrin from fresh vegetables, soon become affected 
with scurvy. 

1191. Animal Nutrition. — It is evident from Para- 
graph 1176 compared with 1190, that much of the ma- 



1189. How is Liebig's extract of meat prepared ? 1190. Why is salted 
meat less nutritious than fresh? 1191. What materials are found ready 
formed in the blood ? 



CIRCULATION OF THE BLOOD. 



587 



terial required to build up the body is found ready 
formed in the blood. It has been transferred to it 
from the vegetable world without material change in 
composition. Thus the fiber which is required for 
muscle, and fat to fill out the tissues, only require to 
be built into their places in the animal frame, as a 
mason lays up a wall from materials provided to his 
hand. For the production of other animal substances, 
essential changes are required. The power of selec- 
tion and appropriation of the proper materials for 
every organ and every secretion, is found to reside in 
innumerable minute cells, which are distributed in 
every part of the body, and endowed with peculiar 
powers according to the offices they are designed to 
fulfill. 

1192. Circulation of the Blood. — In order that all 
parts of the animal frame should 
be built up by the materials con- 
tained in the blood, that fluid is 
carried to every part in a system 
of tubes called arteries, and the 
portion of the blood not thus ap- 
propriated, together with particles 
which have exhausted their vital 
activity, is returned to the central 
organ, the heart, by another series 
of canals called veins. Figure 316 
general view of the circu- 



316 



gives a 




1192. W r hat is the object of the circulation of the blood? Describe 
the general course of the circulation and how it is effected ? 



5S8 ORGANIC CHEMISTRY. 

lation of the blood in the higher animals. The heart 
is a double organ consisting of four cavities or sacs, 
two auricles and two ventricles, contained within the 
dotted circle a ; the vena cava, J, delivers the blood 
and fluids obtained from the digestion of food into 
c, the right auricle which contracts and forces the blood 
into cZ, the right ventricle. The right ventricle con- 
tracts and forces the blood through the pulmonary artery 
e, into f^ the system of minute blood-vessels in the 
lungs ; g is the left auricle which receives the blood 
from the pulmonary veins, or veins of the lungs, and 
delivers it to the left ventricle, A, which then contracts 
and propels it through the aorta, i, to the systemic capil- 
laries, j, from which it is collected by the veins and car- 
ried back to the heart through the vena cava, 5. Dur- 
ing life the blood is constantly flowing through this 
endless circuit, receiving nutrient fluid from the chylif- 
erous ducts, and oxygen from the lungs, distributing 
its nutrient materials to all parts of the system, and 
receiving in return the effete matter of the tissues to 
be carried out of the system. 

Chemical Changes in the Animal Body. 

1193. Certain important changes which are constantly 
occurring in the animal body remain to be considered. 
The body is not the same in any two successive mo- 
ments of its existence. Every breath exhales a portion 
of its substance into the atmosphere, and every effort, 

1193. What is said of changes in the animal body ? 



THE LUNGS. 589 

whether of brain or muscle, is accompanied by some 
transformation in the material of which it is com- 
posed. 

1194. Changes in the Blood. — By comparing the 
blood of animals with their food, it will be evident 
that certain materials have been not only modified, but 
entirely transformed in its production. Starch and 
sugar are important constituents of the food, but they 
form no part of healthy blood. They are transformed 
into fat or other material as soon as they enter the 
circulation, and in this new form constitute the fuel 
from which the heat of the animal body is derived. 
Other changes which occur in the blood will be men- 
tioned in subsequent paragraphs. 

1195. Respiration consists in the introduction of air 
into the animal system, and the removal of gases and 
vapors no longer useful in the animal economy. Respi- 
ration is effected in the lungs, which in the higher ani- 
mals consist of millions of minute air-cells, communi- 
cating with the atmosphere by means of the trachea, 
or windpipe, and its minute branches called bronchi. 

1196. The Lungs completely fill the cavity of the 
chest and by the expansion and contraction of the sur- 
sounding walls they are alternately enlarged and 
diminished in size. When the chest expands by the 
movements of the ribs and diaphragm, the pressure of 
the atmosphere forces the air through the nose or 
mouth and trachea, (windpipe) into the lungs. The 

1194. Mention certain changes in the blood ? 1195. What is respira- 
tion ? 1196. Describe the structure of the lungs ? 



590 



ORGANIC CHEMISTRY. 



317 




subsequent contraction of the chest expels the air. The 
general form and position of the lungs are shown in 

Figure 313. The lungs 
are divided into a multi- 
tude of smaller portions 
called lobules, &, <z, Fig- 
ure 317, each of which 
is supplied with a bron- 
chial tube, <?, c, by which 
it receives air from the 
trachea or windpipe. 
The bronchial tubes 
open into air - cells 
which are seen in clus- 
ters upon their sides and 
ends. The air-cells vary from T ^ to T2 V o of an inch 
in diameter. Their walls are formed of delicate mem- 
brane, continuous with the walls of the branches of the 
bronchial tubes to which they are attached. This mem- 
brane is folded upon itself so as to form a sharp edged 
border at each circular orifice between contiguous air- 
cells or between the cells and the bronchial passages. 
Numerous fibers of elastic tissue are spread out be- 
tween contiguous air-cells, and many of these are 
attached to the outer surface of the membrane form- 
ing the cells, giving them additional strength and 
power of recoil after distension. Outside the cells a 
network of capillary (hair-like) blood-vessels is spread 
out so densely that the interspaces or meshes are even 
narrower than the vessels, which are on an average 



ANIMAL HEAT. 



591 




-j^Ti of an incli in diameter. The arrangement of the 
cells and capillaries is shown in figure 318. Between 
the atmospheric air in 318 

the cells and the blood 
in these vessels, nothing 
intervenes but the thin 
membrane of the cells 
and capillaries and a 
delicate epithelial lining 
of the former. The exposure of the blood to the air 
is the more complete because the folds of membrane 
between contiguous cells, and often the spaces between 
the walls of the same, contain only a single layer of 
blood-vessels, both sides of which are thus at once ex- 
posed to the air. 

1197. Animal Heat. — The oxygen which is necessary 
for the slow combustion of the material above men- 
tioned, (§ 1194), is taken into the blood in the course 
of its passage through the lungs. It passes on with 
them, through the arteries, into the minute capillary 
vessels which are distributed throughout the body In 
these vessels their combination takes place, with the 
same production of carbonic acid and evolution of heat 
as if the material were burned in air or oxygen gas. 
The carbonic acid thus formed is carried back to the 
lungs in the venous blood, and there exhaled through 
the thin membrane of the air-cells, and exchanged for a 
new supply of oxygen gas. In view of the relations 
of starch and sugar to the process of respiration, as 



1197. What is the source of animal heat ? 



592 ORGANIC CHEMISTRY. 

above shown, they have been termed the respiratory 
constituents of the food. 

1188. In cold weather a larger amount of oxygen 
is inhaled with every breath, in consequence of the 
greater density of the air. Eespiration is also invol- 
untarily hastened, and the blood from the two causes 
combined, becomes more thoroughly impregnated with 
oxygen gas. The transformation or combustion of 
the respiratory constituents of the blood, proceeds 
more rapidly in consequence, and more internal heat is 
produced to oppose the external cold. This is one of 
the provisions of nature by which the animal body is 
enabled to resist the influence of the seasons and 
of climate. Labor has the same effect as cold in has- 
tening respiration and necessitating a larger supply of 
food. 

1199. Change in Color of the Blood. — From the 
fact that the globules of the blood undergo a change of 
color in the lungs, where oxygen is absorbed, it is pre- 
sumed that they serve, by absorption of the gas, as the 
medium for its conveyance through the body. As a 
consequence of the changed color of the globules, 
arterial blood is of a bright scarlet, while venous blood 
is dark red. The same change of color which takes 
place in the lungs, may be readily produced by agita- 
ting blood drawn from the veins with air or oxygen 
gas. It is probable that the blood globules serve 
not only as carriers of oxygen to all parts of the sys- 

1198. What is said further of respiration ? 1199. What change of color 
does the blood experience in the lungs ? 



RESPIRED AIR. 



593 



tern, but that they act as the retorts and receivers, so to 
speak, where important changes in the blood plasma 
are effected, by which it is fitted to be built up into 
the various tissues. 

1200. Changes est Kespired Air. — Examination of 
the air expired from the lungs shows that about 5 per 
cent, of the oxygen inhaled has disappeared, and that 
carbonic acid, containing nearly as much combined 
oxygen has taken its place. An increased amount of 
watery vapor is also exhaled, showing that a portion 
of oxygen has united with hydrogen to form water. 
This increase of moisture and expansion by the heat of 
the lungs causes the volume of expired air and vapor 

319 




to be somewhat greater than the amount taken into the 
lungs. Figure 319 shows the method of estimating the 

1200. What changes does air undergo in the lungs? How is this 
shown ? 



594 ORGANIC CHEMISTRY. 

amount of carbonic acid exhaled by a bird or any other 
small animal. The bird is placed in a bell glass, A, 
standing over mercury. The tubes 1 and 2 contain 
pumice stone moistened with a solution of caustic pot- 
ash to absorb all the carbonic acid from the air which 
enters the bell glass ; the bulbs, (7, contain lime water, 
and if it remains clear it is known that the air passing 
through contains no carbonic acid. The vessel, B, con- 
tains water, and as it is allowed to escape, atmospheric 
air is drawn through the tubes, and through the bell 
glass where the bird is confined. The bulbs, D, contain 
caustic potash to absorb the carbonic acid from the air 
expired by the bird. The increased weight of these 
bulbs (weighing them before and after the experiment) 
shows the amount of carbonic acid expired. 

1201. Oxidation throughout the System. — If ani- 
mals are made to respire pure hydrogen or nitrogen, 
they still continue for some time to exhale carbonic 
acid. It is therefore inferred that the oxygen is car- 
ried to all parts of the system in the blood, and that 
the change of oxygen to carbonic acid takes place in 
the capillaries where carbon is taken up from worn-out 
tissues. Through these delicate blood vessels, smaller 
than hairs, the vital fluid courses on, bearing oxygen 
and other nutrient material to the tissues, taking up 
the products of waste, and itself changing from bright 
red arterial to dark venous blood, which returns to the 
lungs for a new supply of the life-bearing oxygen. 

1201. Where is the change of oxygen to carbonic acid and water 
effected ? 



ALL ANIMALS REQUIRE AIR. 595 

1202. Amount of Air Respired. — The average capac- 
ity of the human lungs is reckoned at 225 cubic inches. 
The lungs are never emptied of air, but about 30 cubic 
inches are changed at every respiration. The number 
of respirations varies from 14 to 18 per minute, con- 
suming about 500 cubic inches of air. About twelve 
times this amount of air are required to carry off the 
products of respiration and preserve the atmosphere in 
a suitable condition for the performance of healthy 
respiration. It is thus evident that free ventilation is 
essential to health. 

1203. All Animals require Air. — No animal can 
live without air. Fishes live on air dissolved in the 
water in which they live. Insects breathe through 
elastic tubes opening at their sides. Cold blooded 
animals require but little air, but any animal confined 
in a limited supply of air will soon die. A fish con- 
fined in a jar of water covered with oil can live but a 
short time. A bird or a mouse placed under the re- 
ceiver of an air pump, faints and soon dies if the air is 
exhausted. The continued life of all animals depends 
upon the oxidation of food taken as nutriment. 

1204. Relations of Food and Temperature. — In 
proportion as the draft of a furiface is increased, more 
fuel must be supplied for its combustion. For the 
same reason more respiratory food must be taken into 
the system, in proportion as more atmospheric oxygen 
is inhaled. The fact that a larger quantity is required 

1202. What amount of air is required for healthy respiration ? 1203. 
Why do all animals require air ? 



596 ORGANIC CHEMISTRY. 

in northern climates thus receives a scientific explana- 
tion. The preference entertained in arctic regions for 
certain kinds of food is also accounted for by the same 
necessity for increased resistance to the external cold. 
The train oil and fat which the Greenlander consumes 
with avidity, is a better fuel in the animal body than 
the starch which forms a principal part of the food con- 
sumed in warmer climates. The chemical reason of 
this difference is found in the fact, that starch and 
allied substances contain oxygen and in larger propor- 
tion. They are, as it were, in their natural condition, 
partially burned or oxidized substances. 

1205. Change of the Animal Tissues. — In propor- 
tion to the muscular or nervous activity of the animal, 
the substance of the body is disorganized and returned 
to the blood from which it was produced. From the 
blood it is finally removed by the kidneys, principally 
in the form of urea and uric acid, and thrown off as 
waste material from the system. These substances, 
although organic, may be figuratively regarded as the 
ashes of the consumed muscle and other nitrogenous 
constituents of the body. A portion of the carbon 
and hydrogen of the animal organs has at the same 
time disappeared, like the elements of respiratory food, 
in the form of water and carbonic acid. 

1206. Urea. — Urea, when separated from its solu- 
tion is obtained as a white crystalline solid. Its mole- 



1204. What is said of the relations of food and temperature ? 1205. 
What change takes place in the tissues of the body ? 1206. What is 
said of urea ? 



DISAPPEARANCE OF FAT. 597 

cule contains four atoms of hydrogen, to two each of 
carbon, nitrogen, and oxygen. When left in contact 
with the mucus with which it is accompanied in the 
secretion of the kidneys, it is speedily converted, by 
combination with four molecules of water, into car- 
bonate of ammonia. Urea may also be artificially pro- 
duced from cyanic acid and ammonia. This cyanate is 
identical with urea in composition, and is converted into 
urea by solution in water and evaporation. It was 
among the first of organic bodies artificially produced. 
Uric acid contains the same elements with a larger pro- 
portion of oxygen, and also yields ammonia by its 
decomposition. Besides the above substances, the secre- 
tion of the kidneys contains various soluble salts, which 
have formed part of the body. The insoluble salts are 
removed from the system by other means. 

1207. Disappearance of Fat. — Starvation. — "When 
the supply of respiratory food is deficient, nature avails 
herself of the fat previously stored in the animal body, 
as fuel to sustain the animal heat. It is taken up by the 
blood, and burned in the capillary vessels, as before 
described. This happens in the case of the bear and 
other hybernating animals. Lying dormant during the 
winter season, their fat is consumed, and they emerge 
lean from their dens in the spring. "Where food is 
deficient and there is no accumulation of fat to sup- 
ply its place, the muscle and other portions of the 
body are consumed, and death by starvation is the con- 
sequence. 

1207. What is said of the disappearance of fat? 



598 ORGANIC CHEMISTRY. 

1208. Repair of the Tissues. — As fast as the "worn 
out matter of the muscles and other organs is removed, 
its place is supplied in the healthy body by new mate- 
rial from the blood. Through it, also, the phosphates 
of the soil and the vegetable world are transferred to 
the skeleton of the animal, and in smaller proportion 
to other parts of the frame. The blood is itself re- 
newed by the materials of the food. 

1209. Yarieties of Food. — It is implied in the fore- 
going, that the two classes of substances which enter 
into the composition of the food of animals, subserve 
very different purposes in the animal economy. The 
first class, of which starch and sugar are the principal, 
serve, by their gradual combustion, to sustain the ani- 
mal heat. They are included, as above stated, under 
the general name of respiratory food. The protein 
bodies, on the other hand, all of which contain nitrogen, 
are appropriated in the formation of blood and muscle ; 
they make up the sanguineous or jplastic food. In 
view of the fact that the respiratory food enters also, 
in a changed form, into the composition of the blood, 
the former term can scarcely be regarded as distinctive. 
The latter, which designates the office of the protein 
bodies in furnishing material to build up the organs of 
the body, is much to be preferred. 

1210. Salads and Summer Sours. — Physiological 
research establishes the fact that acids promote the 
separation of the bile from the blood, which is then 



1208. How are the tissues repaired ? 1209. Mention two classes of 
food ? 1210. What is the use of acid fruits as food ? 



PEOPOETIOXS OF FOOD. 599 

passed from the system, thus preventing fevers, the pre- 
vailing diseases of Summer. It is a common saying 
that fruits are " cooling/ 5 and also berries of every 
description ; it is because the acidity which they con- 
tain aids in separating the bile from the blood. Hence 
the great yearning for greens, lettuce and salads, 
in the early Spring, these being eaten with vinegar. 
Hence, also, the taste for something sour, for lemon- 
ades, on an attack of fever. But, this being the case, it is 
easy to see that we nullify the good effects of berries in 
proportion as we eat them with sugar, or even with 
sweet milk or cream. If we eat them in their natural 
state, fresh, ripe, perfect, we are not likely to eat too 
many, or to eat enough to hurt us, especially if we 
eat them alone, and not taking any liquid with them 
whatever. 

1211. Proportions of Food. — For the economical 
sustenance of animals, it is of importance that a proper 
relation of quantity should be maintained between 
these two varieties of food. Respiratory food alone, 
provides no material for supplying the waste of the or- 
ganized tissues. Plastic food, on the other hand, is 
especially adapted to this end, but it* is poor fuel for 
sustaining the heat of the body. Tet in lack of other 
material, it is diverted from its natural use, and thus 
appropriated at great economical disadvantage. 

1212. Nature teaches us something on this subject, in 
the composition of milk and those grains which consti- 

1211. What is said of the importance of due proportion of the two 
kinds of food ? 1212. W 7 hat does nature teach on this subject ? 



600 ORGANIC CHEMISTRY. 

tute the principal food of man. It will be found by 
reference to the table in the Appendix, that the quan- 
tity of respiratory matter in these substances, is from 
three to six times greater than that of the plastic mate- 
rial. When the object is to fatten an animal, the pro- 
portion of respiratory matter may be considerably 
increased by the use of potatoes, rice and other farina- 
ceous food. Being furnished in excess, it accumulates 
in the body in the form of fat. Working animals, on 
the other hand, must be supplied with nitrogenous or 
plastic food in large proportion. The use of bacon 
with peas, beans, and eggs, and many other popular 
mixtures of food, are accounted for on the principle 
above stated. For the development of most of the 
views presented in this chapter, the world is indebted 
to the distinguished Liebig. 



CHAPTER IV. 

CIRCULATION OF MATTER. 

1213. The relations of the three kingdoms of nature 
have been already incidentally considered in former 
parts of this work. It remains to present the subject 
in a single view. It is obvious, at a glance, that the 
soil does not furnish all the material which is required 
for the wants of vegetable life. The level Qf our mead- 
ows is not lowered by removal of successive crops, nor 
does the forest dig its own grave at its roots as it lifts 
its ponderous trunks into the air. The atmosphere, 
as well as the soil, contributes to the increase of mass, 
whether of wood or grain, and indirectly feeds all races 
of animal existence. The relation of the three king- 
doms of nature is thus established. 

1214. Water is one of the principal agents in the 
system of circulation of matter, which constitutes the 
life of the globe we inhabit. In the fulfillment of its 
office, it passes incessantly from sky to earth, now 
mingling with the currents of the atmosphere, and 
anon with those which form the arteries and veins of 



1213. What proves the relation of the three kingdoms of nature ? 
1214. How does water serve in the circulation of matter ? 

26 



602 OKGANIC CHEMISTRY. 

the great world of waters. Lifted into the atmosphere 
by the sun, it descends again in dew and rain, corrod- 
ing and dissolving the rocks on which it falls, and dis- 
tributing them widely over land and sea. 

1215. It settles through the stony crust of the earth, 
into the dark recesses of the rocks where crystals blos- 
som out of the formless stone, and supplies them with 
the material for their wonderful architecture. It pene- 
trates the soil, and supplies the same material to the 
roots of plants for the still more wonderful creations of 
leaf, and fruit, and flower. Again it hastens through 
brooks and rivers on its course, and pours its burden 
into the sea, for the use of the innumerable forms of 
vegetable and animal life which inhabit its waters. 
The coral insects build up solid islands out of the mat- 
ter it provides. Countless shell-fish clothe themselves 
in the same rocky garments, and finally cast them aside, 
to be buried under the slime of the sea and harden, in 
the course of ages, into stone. The water which has 
served these various offices, climbs anew into the 
heavens upon the solar rays, and again descends in 
the rain, repeating forever its round of service to the 
earth. 

1216. The further relations of the three kingdoms of 
nature may be presented in a single picture. Imagine 
a giant tree, the representative of all the vegetation of 
the earth, spreading wide its branches as a shelter for 
man and beast. Let us suppose them to subsist en- 

1215. What distinct office does it fulfill ? 1216. How may further rela- 
tions of the three kingdoms be illustrated ? 



CIRCULATION OF MATTER. 603 

tirely upon its fruit, and to warm themselves by fires 
made from its branches. The tree, through its leaves, 
draws its supply of gaseous food from the atmosphere, 
and through its roots, its mineral sustenance from the 
soil. It has purified the air in the process, of gases 
which would become noxious by accumulation, and 
returned to it the oxygen which is the vitalizing breath 
of the animal world. The mingled material of its 
food, worse than worthless to animals, has, at the same 
time been transformed into wood and fruit, and other 
forms of vegetable matter. 

1217. At this point, without interruption in the cir- 
cuit, commences the return of material to the atmos- 
phere from which it was derived. Animals that feed 
upon the fruit of the tree, already breathe much of it 
back again to the air while they live, and the rest is 
restored by their death and subsequent decay. Leaves 
that fall and moulder, and branches that are burned as 
fuel, make the same return of the elements of which 
they are composed, to the great reservoirs of the at- 
mosphere and earth. And what happens thus to leaf 
and fruit, happens also at last to the parent tree itself. 
One by one its giant branches fall and moulder, and 
melting again into the air, add to its inexhaustible 
stores of fertility, and provide the material for a new 
round in the grand system of circulation. 

1218. What happens beneath the single tree, occurs 
also in every flower that lifts its petals to the sun, and 

1217. Explain the return of matter to the atmosphere ? 1218. Hlus- 
trate the extent of these relations ? 



604 ORGANIC CHEMISTRY. 

is a thousand times repeated in every forest upon the 
face of the earth. No limits of distance or of size 
restrict the mutual relations and dependencies of na- 
ture. The exhaled carbon of the polar bear feeds the 
lotus of Egyptian plains, and the breath of the southern 
lion is redistilled in the fragrance of the Norwegian 
pine. The particle of matter that once burned in the 
fire of the poet's brain and floated with his song upon 
the air, now blooms in the mountain flower and anon 
lies buried in its mould. 

1219. According to the view thus presented, it will 
be seen that the sun is the great material source of the 
life of the world. He wings the vapors that rise from 
the sea, and fall again to make their ministering circuit 
in the earth. The solar rays are the agents also, in the 
transformation of matter, which takes place in every 
leaf and blossom, and provides the animal kingdom 
with its food. 

1220. No less is the sun the source of all the mechan- 
ical power which is known upon the earth. The falling 
flood of Niagara is but the recoil of the spring which 
is bent in evaporation from the sea and earth. All 
force which is derived from the fall of water, is thus 
traceable to the sun, which lifted it in the form of cloud 
and vapor. The energies of fire and steam, are only 
other forms of the force inherent in the solar rays, 
originally exercised in the organization of the vegetable 
matter which serves as fuel. Immediately produced 

1219. What is the material source of the life of the world? 1220. 
Show how it is the source of mechanical power ? 



CIRCULATION OF MATTER. 605 

by oxidation and the heat which it evolves, they find 
their ultimate source, as well as their precise equivalent, 
in the deoxidizing influence of the solar rays. The 
forces of the human body are fed by consumption of 
similar materials, and may therefore be traced to the 
same source. 

1221. Every planet that surrounds with its orbit the 
great centre of our system, is equally dependent upon 
his influence. Held in their courses by his attraction, 
and encircling him in ceaseless revolution, they draw 
from the parent orb the strength and beauty which 
clothes their lesser spheres. What wonder, that in 
vague acknowledgment of his influence, heathen have 
acknowledged the sun as their God, and worshiped at 
his shrine. How natural that Christian nations should 
find in his life-giving power, a fitting emblem of the 
glory and beneficence of the great Father of the Uni- 
verse, by whom all suns and systems, are, and were 
created. 

1221. What further influence has the sun ? 




APPENDIX. 



In this Appendix are included formulas descriptive of chemical 
reactions, and other matter no less important, the introduction of 
which into the text would have interferred in a measure with the 
plan of the work. 

The formulas constitute a precise statement, in the language of 
the symbolical nomenclature, of the reactions already described in 
more general terms. It is not to be understood from the formulas 
that the materials concerned in any process must always be brought 
together in the precise proportions indicated in the first member of 
the equation. One or the other may be in excess ; if so, the 
excess is null, and not considered in the formula. The latter re- 
gards and indicates only the relative quantities which are actually 
concerned in each reaction — the first member having reference 
to the materials employed, and the latter to the products. 

Interpreted according to the atomic theory, each formula gives 
on the one side of the equation, the nature and relative number 
of the atoms or molecules which take part in any reaction, and 
on the other, the nature and relative number of those which 
result. 

The student will do well, as an occasional exercise, to calculate 
from the formulas the relative quantities of materials required in a 
reaction, and of products resulting from it in pounds and ounces. 
A T in the tables stand respectively for acetic and tartaric 
acids. 

§ 172. The numbers given in the text are only approximations. 
The exact quantities may be readily calculated by the law of ex- 
pansion and contraction of gases and vapors previously given, 



APPENDIX. 



607 



taking the volume of steam at 212° (§ 205,) as a starting 
point. 

§ 290. Active Force of the Voltaic Current. — The intensity 
of the current increases with the number of couples of which the 
battery is composed. 

When the exterior resistance to be overcome is great, as when 
it passes through a long wire, or through bad conductors, the 
increase of intensity by increasing the number of couples is very 
evident. If the poles of the battery are united by a perfect con- 
ductor, or by one so short that its resistance may be regarded as 
nothing, then a single pair of plates gives as great intensity as a 
series of many pairs of plates. Hence for displaying the voltaic 
arch or for telegraphing or decomposing chemical compounds, a 
battery of many plates is required. But if the exterior resistance is 
small, the best effect is obtained with a battery consisting of a few 
large plates, or what has the same effect by uniting all the poles 
of the same name together, so that they may act as a single 
pair. 

§ 293. Smee's Battery. — Of all the batteries in common use, 
Smee's, which is represented in the figure, is 
the simplest. It consists of a plate of silver, 
with plates of zinc hanging near it on either 
side. The two zinc plates communicate with 
each other by a metallic connection, and are, 
therefore, but one plate. It is found best to 
roughen the silver with platinum black. 
Smee's batteries are commonly sold in thi3 
condition. The clamp and bar are simply to 
keep the plates in place. Water acidulated 
with from one-seventh to one-sixteenth of 
its bulk of oil of vitriol, is employed in this 
battery. It is generally used in plating. 

In explaining the action of sulphuric acid in this battery, it is 
best to regard it as composed of the radical S0 4 and Hydrogen 
(p. 364). Substituting S0 4 H for C1H, the explanation given in 
paragraph 288 of the text applies to this case also. 

Groves' Battery. — In Groves' battery the metal platinum is 
used instead of copper or silver. It is placed by itself in a porous 




608 



APPENDIX. 



earthen cup containing nitric acid. The vessel is placed in a 
larger one containing zinc and sulphuric acid. The two acids mix , 
to some extent through the pores of the inner cup, so as to com- 
plete the circuit by their contact. Without this the battery could 
not operate. No hydrogen is evolved in this battery. Traveling 
along from the zinc in successive decompositions (288), it comes 
upon N0 5 , at the point where the two acids meet. H 3 here com- 
bines with 3 of the N0 5 , and the residual N0 2 takes 2 from 



324 




the next N0 5 . This action continues until the platinum surface is 
reached where N0 2 is evolved, changing to red fumes of hyponitric 
acid in the air. 

Figure 324 shows a similar battery in which the platinum in the 
inner cylinder is replaced by a cylinder of carbon. It is shown in 
action decomposing a solution of sulphate of soda in an infusion of 
violets ; the acid going to the positive pole gives the solution a red 
color and the alkali going to the negative pole colors the solution 
green. 



The Ruhmkorff Coil is an apparatus for changing dynamical or 
Voltaic electricity into statical electricity, giving powerful shocks 
like the electricity produced by friction. 

If an insulated wire is placed very near and parallel to the wire 
connecting the poles of a Voltaic battery a secondary current will 



APPENDIX. 609 

be excited in the insulated wire which will move for an instant in 
a direction opposite to the motion of the current from the battery. 
On breaking the circuit of the battery wire a current again moves 
over the insulated wire of greater intensity than before but in the 
same direction that the battery current was previously moving. 
These effects are more obvious when the insulated wire is of great 
length wound in the form of a helix surrounding a similar helix 
formed of the wire which unites the poles of the battery. The ef- 
fect is also greatly increased by placing a bundle of soft iron wire in 
the inner helix so that it shall become an electro-magnet as often as 
the poles of the battery are united. In the Euhmkorff coil as now 
constructed the insulated wire is from thirteen to twenty miles in 
length laid up in the form of a helix surrounding a helix of larger 
wire through which the battery current passes. The inner helix 
incloses a bundle of iron wire, and the two helices are carefully insula- 
ted from each other by a glass cylinder and gutta percha. The ap- 
paratus has also a contrivance for making and breaking contact with 
great rapidity which also heightens the effect. With such a coil a 
torrent of electric sparks can be projected through free air when the 
ends of the insulated wire are separated nine inches, and with some 
instruments even twenty inches. Small animals are instantly killed 
by these discharges, and dangerous effects are produced upon the 
human system by the same means. All the phenomena usually 
produced by the most powerful plate electrical machine may be 
produced by the Euhmkorff coil. If the two ends of the insulated 
wire terminate in electrodes inclosed in a vacuum tube or flask the 
electric light is developed in interrupted bands which present a close 
resemblance to the Aurora Borealis. All the phenomena of lumi- 
nous electricity may be exhibited with this apparatus. 

§ 317. The Atomic Theory.— That combination takes place in 
definite and multiple proportions, is directly proved by experiment. 
Oxygen, for example, unites with hydrogen in the proportion of 
8, 16, 32, and 40, to one of the latter element, and refuses to com- 
bine in any other proportion. If matter were infinitely divisible, 
no reason could be assigned for this fact. Each infinitesimal por- 
tion of oxygen possessing the same affinities, we should expect to 
find combination in exact proportion to the quantity supplied. 



610 APPENDIX. 

Dalton's atomic theory, the truth of which is assumed in the 
text, affords a luminous explanation of the facts under considera- 
tion. According to this theory, oxygen combines with hydrogen 
in no smaller proportion than that of 8 to 1, because this is the 
ratio of weight in the least existent particles of the two substances. 
It combines in the proportion of 16, 24, 32, and 40, by uniting 2, 
3, 4, or 5 of its atoms to one of hydrogen. It refuses to combine 
in any intermediate ratio, because its atoms are indivisible. The 
same view of the constitution of matter is essential to the explana- 
tion of innumerable facts in organic chemistry. 

The value of a table of atomic weights does not depend in the 
least degree upon the reception of the atomic theory. It is a list 
of combining proportions, determined by careful analysis, and re- 
duced to a simple standard of comparison. Its truth is independent 
of all theory. 

Kelations of Atomic Weight and Density. — The comparative 
weight of equal measures or masses of different substances is not 
necessarily the same as the comparative weight of their atoms. 
The mass of iron, for example, is heavier, while the atom of iron is 
lighter than that of potassium. To account for the fact, we must 
suppose the lighter atoms of iron so closely arranged that they thus 
more than make up by their larger number, for their inferior weight. 
In solids generally, there is no correspondence between atomic 
weight and specific gravity ; but in the case of many elements 
which exists in the gaseous state, or are capable of assuming it, the 
correspondence is complete, as shown in the following paragraph. 

Combining Measures or Equivalent Volumes.— When oxygen 
and hydrogen gases combine in the ratio of their atomic weights, 
it is found that the volume of hydrogen which has entered into the 
combination is just double that of the oxygen. But in general, 
where elementary gases combine in the ratio of their atomic weights, 
equal volumes take part in the combination. This rule will become 
nearly universal for this class of substances if we regard the atomic 
weights of nitrogen, phosphorous, chlorine, and a few other elements 
as half that now assumed. We must assume at the same time that 
two atoms with the new weight exist in all compounds in place of 



APPENDIX. 611 

every single atom of the old weight. The formula of water, for ex- 
ample, will become H 2 0, and that of nitric acid N 2 3 . The for- 
mulas thus changed will indicate as before in all cases the true com- 
position by weight. According to this view the elementary gases 
contain in equal volumes the same number of atoms. This follows 
from the fact that the proportional weight of equal volumes of the 
different gases is the same as the proportional weight of individual 
atoms of the different gases. One advantage of this view among 
others is that it introduces great simplicity into our conception of 
the gases. It presents them to us as consisting of atoms equal in 
volume ; equal also in specific heat. It also furnishes us with num- 
bers for the atomic weights which express at the same time specific 
gravity and combining volume. 

In the production of compound gases, the elements either suffer 
no condensation or experience a very simple change of volume. 
Thus hydrochloric acid gas, formed by the combustion of hydrogen 
and chlorine, possesses the united volumes of its constituents. 

Equivalent Volumes of Compound Gases. — As the equivalent 
or combining proportion of a compound is equal to the sum of the 
equivalents of its constituents, it follows that the combining meas- 
ure of hydrochloric acid is equal to the sum of the combining meas- 
ures of hydrogen and chlorine, 2 + 2=4. Ammonia is formed by 
the union of three volumes of hydrogen and one of nitrogen. Con- 
densation takes place to the amount of i of the whole volume of 
their mixed gases. The combining measure is therefore equal to 
the sum of the combining measures of the constituents divided by 
2. The sum of the combining measures is 8. 8-^2=4. Steam is 
composed of one combining measure (two volumes) of hydrogen, 
" united with one combining measure or volume of oxygen, and con- 
densed to two volumes in combination. Its combining measure is 
therefore 2. The above instances may serve as examples of the in- 
teresting relations of atomic weights, specific quantity and combin- 
ing measures. 

Calculation of Specific Gravity. — The density or specific grav- 
ity of a compound vapor or gas of known proportional composition, 
may be readily calculated from that of its constituents, supposing 



612 AP P ENDI X. 

the amount of condensation which takes place in their combination 
to be known. The results thus obtained are more accurate than 
any results of experiment. In like manner the proportional com- 
position of a compound may be calculated from a knowledge of its 
elements and density. The density of the vapor of carbon and the 
other solids which are not known in the gaseous form, may be cal- 
culated from the density of their compounds with elementary gases 
of known density. That of carbon, for example, may be deduced 
from that of carbonic acid. The calculation involves an assumption 
as to the equivalent volume of carbon. Assuming it to be the same 
as that of hydrogen, the density of carbon vapor is 423.4. If its 
equivalent volume is the same as that of oxygen or \ that of hy- 
drogen, the density is doubled. 

Atomic Volumes. — It is obvious that the number of atoms of a 
given weight in any mass, must be in proportion to the density of 
the mass. The size of the same atoms must be less in the same 
proportion. The atomic volume of any substance is therefore ob- 
tained by dividing the atomic weight by the density or specific 
gravity of the body. The subject of atomic volumes has important 
relations to the science of crystallography. In comparing atomic 
volumes it is assumed that the space which a body occupies is com- 
pletely filled by the atoms, without intervening space. 

Atomic Heat. — The numbers 28, 32, 103, represent, in the order 
in which they are given, the atomic weights of iron, copper, and 
lead. It is a remarkable fact that if the three metals be taken in 
these relative proportions, it will require the same expenditure of 
heat to make them equally hot, 103 pounds of lead can be heated 
up to 212°, for example, by burning the same amount of alcohol 
which will heat 32 pounds of copper, or 28 pounds of iron, to the 
same degree. Most other metals, and the non-metallic element sul- 
phur, come into the same class, or in other words, have the same 
atomic heat. The atomic heat of arsenic and silver is double that 
of the elements above mentioned. Other elements are different in 
this respect, but commonly by some simple ratio of difference. The 
correspondence is never absolute, but so close as to have led 
many chemists to attribute the variations to errors of experiment, 



APP END I X. 



613 



and to regard the law of correspondence of atomic heat as uni- 
versal. 

§ 333. When the same element unites with oxygen in different 
proportions to form different acids, these are distinguished by pre- 
fixes and terminations which indicate the order in which they stand 
to each other with respect to the quantity of oxygen. 

The first acid of such a series discovered, generally receives the 
termination " ic." Chloric acid may serve as an example. Another 
acid compound of chlorine since discovered, and containing more 
oxygen, is called hyperchloric, signifying higher than chloric. The 
other names of the list indicate, by their prefixes and terminations, 
the order of oxygenation of the several acids. The same means 
of distinction are employed in other series. 

Hypochlorous acid CIO. 

Chlorous acid . . . . 9 C10 2 . 

Hypochloric acid, (peroxide of chlorine,) C10 4 . 

Chloric acid C10 5 

Hyperchloric acid C10 7 . 

§343. KO, CI0 5 = KCl + 60. 

§347. 3Fe + 40=Fe 3 4 . 

§351. P + 50=P0 5 . 

§353. C + 20=C0 2 . 

§365. 2HCl + Mn0 2 =2HO + MnCl + Cl. 

§ 368. (CaCl + CaO, C10) + 2S0 3 =2(CaO, S0 3 ) + 2C1. 

§371. Sb + 5Cl=SbCl 5 . 

§ 375. It will be observed, on comparing § 375 with those which 
precede, that chlorine sometimes expels oxygen, and is sometimes 
expelled by it. In relation to the apparent inconsistency of these 
facts, little more can be said than that chemical affinities are modi- 
fied by circumstances, the action of which is not perfectly under- 
stood. 

§378. HO + Cl=HCl-fO. 

§ 388. NaI + 2S0 3 +Mn0 2 =NaO, S0 3 +MnO, S0 3 +I 

§399. S + 20=S0 2 . 

§ 422. Zn + HO, S0 3 =ZnO, S0 3 +H. 
Cu + 2S0 3 =CuO, SO3 + SO0. 

§429. P + 50=P0 5 . 

§430. Cu + 0=CuO. 



614 



APPENDIX, 



325 



§441. 

§442. 
§443. 
§447. 
§450. 
§466. 



§504. 
§514. 
§ 516. 
§522. 
§528. 
§550. 
§552. 
§561. 
§568. 
§570. 
§574. 




§ 437. Liebig's Potash Bulbs shown at J?, Figure 117, are shown 
on a larger scale in Figure 325. 
They are partly filled with a solu- 
tion of caustic potash. As the air 
is driven through the apparatus 
the first bulb m is emptied, but it 
remains at a, 5, c, d, e, and /, and 
as the air passes from bulb to bulb 
it is entirely deprived of carbonic 
acid. 

§440. KO, NO s +HO, S0 3 = 
KO, SO 3 + HO, N0 5 . 
3Cu + 4N0 5 = 3(CuO, 
HD A ).+HO* 

3Sn + 2N0 5 =3Sn0 2 + 2N0 2 .^ 
N0 2 +20=N0 4 . 
3P + 51Sr0 5 =3P0 5 + 5ISr0 2 . 
5C + P0 5 =5CO + P. 

AsCl 3 + 6Zn + 6(110, S0 3 ) = 6(ZnO, S0 3 + 3HC1 + 
AsH 3 . 
§485. C + 20=C0 2 . 

§486. HCl + CaO, C0 2 =H0 + CaCl + C0 2 . 
§501. C0 2 + C=2CO. 

C 2 8 , HO + S0 3 =HO S0 3 + C0 2 + C0. 
Zn-f S0 3 +H0 2 =ZnO, S0 3 +H. 
3Fe+4HO=Fe 3 4 +4H. 
H+0=HO. 
Na + HO=lSraO+H. 
H + C1=HC1. 

HO, S0 3 +NaCl=:NaO, S0 3 + HC1. 
Si0 3 +3HF=3HO-fSiF 3 . 
N + 3H=NH 3 . 

CaO+NH 4 Cl=HO + CaCl+NH 3 . 
NH 3 +H01=NH 4 OL 
§ 577. KO + 3HO + 2P=KO, P0 3 +PH 3 . 
§ 584. 2S0 3 +C 4 H 3 2 =2(HO, S0 3 ) + C 4 H 4 . 
§ 624. 2C + KO, C0 2 =3CO + K. 
§ 635. Na + NH 4 01 + Hg=NaCl + NH 4 , Hg. 



"* 



APPENDIX. 615 



§682. Sb + 5Cl=Sb01 s . 

- pq R ( Litharge =PbO. 

% - \ Red Lead=Pb 3 4 . 

§ 739. The other elements not mentioned in the text are lithium, 
caesium, rubidium, thallium, ilmenium, glucmum, cadmium, cerium, 
columbium or tantalum, didymium, erbium, iridium, lanthanum, 
molybdenum, niobium, norium, osmium, palladium, pelopium, rho- 
dium, ruthenium, selenium, tellurium, terbium, thorium, titanium, 
tungsten or wolframium, vanadium, ytrium and zirconium. With 
the exception of selenium and tellurium, which are analogous in 
their properties to sulphur, they may be classed with the metals. 
They are of rare occurrence, and may be regarded as sustaining the 
same relation to the other elements as do the asteroids and satel- 
lites to the more important members of the solar system. Caesium, 
rubidium and thallium are new metals discovered by the use of 
the spectroscope. 

§ 704. Zn + PbO, A=ZnO, A+Pb. 

§724. NaCl + AgO,N0 5 =NaO,NO«+AgCl. 

§ 785. CaO, HO + KO, C0 2 = CaO, C0 2 +K0 HO. 

§ 792. NH 3 + HO, S0 3 =NH 4 0, S0 3 . 

§ 793. CaO, C0 2 = C0 2 + CaO. 

§ 794. CaO + HO = CaO, HO. 

§808. HCl + N"aO-=HO + XaCl. 

§ 809. KTaCl + AgO, N0 5 =NaQ, X0 5 +AgCl. 

§ 815. (CaCl + CaO, C10) + 2C0 2 =2(CaO, C0 2 ) + 2CL 

§ 818. 2CaO + 2Cl=(CaCl + CaO, CIO). 

§819. 3C + 3Cl + Alo0 3 =3CO + AloCl 3 . 

§ 827. HO, S0 3 +CaF=CaO, S0 3 +HF. 

§ 829. PbO, A + HS=HO, A + PbS. 

§ 836. NaO + S0 3 =NaO, S0 3 . Vide § 422. 

§ 837. (CaO, S0 3 + 2HO)-2HO + CaO, S0 3 . 

§838. 2HO + CaO, S0 3 = (CaO, S0 3 +2HO). 

§840. HO, S0 3 +XaCl=HCl + tfaO, S0 3 . 

§ 844. (KO, S0 3 +A1 3 3 , 3S0 3 +24HO)=24HO + (KO, S0 3 + 
Al o 3 , 3S0 3 ). 
r Sulphate of Zinc=(ZnO, S0 3 + 7HO). 

§ 847. ) Sulphate of Copper = (CuO, S0 3 + 5HO). 
t Sulphate of Iron=(FeO, S0 3 + 7HO). 

§ 851. CaO, N0 5 =KO, C0 2 =CaO, C0 2 4-KO, N0 5 . 

§853. S + KO, XO = +3C=ks + X + 3CO z . 



616 APPENDIX. 

§ 855. NH 4 0, N0 5 =4HO+2NO. 

§ 859. KO, C0 2 +Ca0, N0 3 ==KO, N0 5 + CaO, C0 3 . 

§ 862. CaO, c6 2 +NaS=CaS + NaO, C0 2 . 

§ 871. CaO + C0 2 =CaO, CO.. 

§876. (2NaO, HO, P0 5 +24HO) + 3(AgO, N0 5 )=2(NaO, N0 5 ) 
+ H0, N0 5 +24HO + 3AgO, P0 5 . 

§902. KO, C0 2 +2(PbO, Cr0 3 ) = KO, Cr0 3 + C0 2 +2PbO > 
Cr0 3 . 

§ 906. 3 (KO, Mn0 3 ) +2S0 3 = 2(KO, S0 3 ) + Mn0 2 + KO, 
Mn 2 7 . 

§ 949. During the night a reverse process of absorption of oxy- 
gen and exhalation of carbonic acid takes place, to a small extent. 

§ 1153. Mode of Estimating the Value of Guano, etc. — In 
estimating the money value of guano for agricultural purposes, 
ammonia maybe set down at 16 cents per pound, potash at 4 cents, 
and phosphoric acid at li to 2 cents. As far as the latter exists in 
a soluble form, its value is doubled. Other substances are of so little 
comparative value that they need not be taken into the account. 
These valuations are based, not alone on their relative value as fer- 
tilizers, but on the cost of the different substances when obtained 
from other sources. They are somewhat arbitrary, but may serve 
as a means of approximate estimation of the value of guano and 
other fertilizers. 

As an average of the composition of thirteen samples of Peruvian 
guano, Professor "Way obtained the following results: ammonia, 
17.41 per cent.; phosphoric acid, 11.13; potash, 3.50. This would 
seem to be considerably above the ordinary average. The pecu- 
niary value of such an article, according to the above valuation, 
would be $63.00 per ton, of which $55.60 would lie in the ammonia. 
No distinction is made in the potential and actual ammonia of 
guano, because the conversion of the former into actual ammonia 
takes place so rapidly in the soil. But the potential ammonia of 
most nitrogenous substances, as of clippings of hides and other sim- 
ilar refuse, is to be estimated at least 25 per cent, lower, in view of 
their comparatively slow conversion. 

In all analyses of concentrated fertilizers excepting guano, in 
which the first distinction may be neglected, the amount of actual 
and potential ammonia, of soluble and insoluble phosphoric acid 



APPENDIX. 



617 



and of potassa, should be separately stated. The latter constituent 
is, however, of comparatively little importance. The farmer who 
purchases his artificial fertilizers without a skillful and well attested 
analysis, is at the mercy of the ignorant or unscrupulous dealer. 

TABLE I. 

LINEAR EXPANSION OF SOLIDS ON BEING HEATED FROM 32° to 212° F. 



Zinc (cast) 


expands 


1 

323 


Iron expands -gj^ 


Zinc (sheet) 


a 


* 1- 
34 


Steel (tempered) H -g } 2 


Lead 


a 


1 

351 


Steel (untempered) " 5^ 


Silver 


tt 


l 

524 


Platinum " ^, 


Copper 


it 


1 
5 81 


Flint G-lass " j^i 


Gold 


it 


1 

882 


Black Marble " -a^ 



TABLE II. 

PECIFIC HEAT. 

Waters 1.000. 



Alcohol 0.660 

Ether 0.520 

Nitric Acid 0.442 

Oil of Turpentine 0.425 

Sulphuric Acid 0.333 

Carbon 0.241 

Common Salt 0.225 

Lime 0.205 

Sulphur 0.202 

Glass 0.197 



Phosphorus 0.187 

Iron 0.113 

Zinc 0.099 

Arsenic 0.081 

Tin 0.056 

Iodine 0.054 

Silver 0.050 

Mercury 0.033 

Platinum 0.032 

Gold 0.032 



TABLE III. 

MEETING POINTS OF SOLIDS. 



melts 



Cast Iron, 
Cobalt 

Silver " 

Gold " 

Copper " 

Lead " 

Bismuth " 

Tin " 

Sulphur u 
Newton's Alloy " 

Sodium " 



at 


3479° 


a 


2800° 


a 


2283° 


tt 


2016° 


tt 


1996° 


it 


612° 


it 


497° 


a 


442° 


a 


226° 


it 


208° 


it 


194° 



Potassium melts at 


154° 


Wax 


u 


u 


142° 


Spermaceti 
Phosphorus 
Tallow 


tt 

a 


a 
a 

it 


112° 

108° 
92° 


Olive Oil 


tt 


tt 


36° 


Ice 


u 


u 


32° 


Oil of Turpentine 
Mercury 
Liquid Ammonia 


a 
a 
tt 


it 
tt 
tt 


-14° 
-39° 
-40° 


Ether 


a 


tt 


-47° 



618 



APPENDIX. 



TABLE IV. 

BOILING POINTS OF LIQUIDS. 



Mercury 


toils at 


662° 


Nitric Acid 


boils at 248° 


Whale Oil 


a it 


630° 


Water 


a u 212° 


Sulphuric Acid 


a a 


620° 


Alcohol 


u u !7 3 o 


Sulphur . 


u a 


600° 


Bromine 


U it 116 o 


Phosphorus 


u u 


551° 


Ether 


" " 96° 


Oil of Turpentine " " 


312° 


Sulphurous Acid 


" " 14° 



TABLE V. 

COMPOSITION OF HUMAN BLOOD ACCORDING TO LECANU. 



Water 78.015 

Fibrin , 0.210 

Albumen 6.509 

Blood-globules 13.300 

Crystallizable fat 0.243 

Oily fat 0.131 

Salts of the alkalies 0.837 

Salts of earths and oxide of iron 0.210 

Othei substances 0.545 

100.000 



TABLE VI. 



COMPOSITION OF COW S MILK. 



Water. 873.0 

Casein, and a little albumen 48.2 

Butter 30.0 

Sugar of milk 43.9 

Phosphate of lime with a little chloride of calcium 2.3 

Phosphate of iron and magnesia, and a little soda 0.9 

Chlorides of sodium and potassium t . 1.7 

1000.00 



APPENDIX. 

TABLE VII, 



619 



RELATIVE PROPORTIONS OF THE SANGUIGENOUS TO THE RESPIRATORY 
CONSTITUENTS IN DIFFERENT KINDS OF FOOD. 



„ 


8a 


iguigenous. 


Respiratory. 




Cow's milk 


contains, for 10 


oq j 8.8 fat and 

~~ \ 10.4 milk sugar 


Human milk 


u 


10 


40 




Horse beans 


ti 


10 


22 




Peas 


it 


10 


23 




Fat mutton 


u 


10 


27=11.25 fat 


Fat pork 


tt 


10 


30=12.5 


tt 


Beef 


a 


10 


17=7.08 


tt 


Veal 


it 


10 


1=0.41 


ti 


Wheat flour 


a 


10 


46 




Oatmeal 


a 


10 


50 




Rye flour 


it 


10 


57 




Barley 


u 


10 


57 




Potatoes (white) 


it 


10 


86 




Potatoes (blue) 


it 


10 


115 




Pice 


a 


10 


123 




Buckwheat 


a 


10 


130 


■ 



Starch is the principal constituent of respiratory food in the sub- 
stances mentioned in the table. When sugar and fat take its place, 
the fact is separately indicated, while their equivalent in starch is 
given in the principal column for convenience of comparison. The 
above table is taken from Liebig's Letters on Chemistry. 

TABLE VIII. 

PER CENT. BY MEASURE, OF ALCOHOL IN SPIRITUOUS LIQUORS AT 62° F. 



Rum 




contains 


72 to 77 per cent. 


Cognac 




u 


50 " 54 


a 


Whiskey 
G-eneva 




It 
It 


59 
50 


u 
a 


Port wine 


a 


21 to 23 


u 


Sherry 
Madeira 


tt 


a 
it 


15 " 25 
18 " 22 


a 
a 


Malmsey 
Claret 


It 
ti 




16 

9 to 15 


a 
a 


Burgundy 
Rhenish 


a 
a 


it 

a 


7 " 13 

8 u 13 


a 


Moselle 


a 


ti 


8 " 9 


a 


Tokay 
Champagne 


a 
it 


tt 

a 


9 

5 to 15 


a 



620 



APPENDIX. 



TABLE IX. 

SOLUBILITY OF SUBSTANCES 





KO 


JSTaO 


NH 4 


BaO 


SrO 


CaO 


MgO 


A1 2 3 


MnO 


FeO 


NiO 






1 


1 


1 


1 


i2 


2 


2 


2 


2 


2 


s 




1 


1 


1 


1 


i2 


2 




2 


2 




CI 




1 


1 


1 


1 


1 


1 


1 


1 


1 


1 


I 




1 


1 


1 


1 


1 


1 




1 


1 




so 3 




1 


1 


3 


3 


1 2 


1 


1 


1 


1 


1 


N0 5 




1 


1 


1 


1 


1 


1 


1 


1 


1 


1 


P0 5 




1 


1 


2 


2 


2 


2 




2 


2 


2 


co 2 




1 


1 


2 


2 


2 


2 




2 


2 


2 


c 2 o 3 




1 


1 


2 


2 


2 


2 


2 


2 


1 2 




B0 3 




1 


1 


2 


2 


2 





2 


2 


2 


2 


A 




1 


1 


1 


1 


1 


1 


1 


1 


1 


1 


T 




1 


1 


2 


2 


2 


1 2 


1 


i2 


1 2 




As0 5 




1 


1 


2 


2 


2 


2 


2 


2 


2 


2 


As0 3 




1 


1 


2 


2 


2 








2 


2 


0r0 3 




1 


1 


2 


2 


2 


1 


2 


1 




2 



EXPLANATION OF THE TABLE. 



To ascertain the solubility or insolubility of a salt from the above 
table, its acid is sought in the left hand column, and its base in 
the upper line. The square, which is in line with both, contains 



APPENDIX. 



621 



TABLE IX.— (Continued.) 

IN WATER AND ACIDS. 





ZnO 


PbO 


SnO 


Sn0 2 


Bi0 3 


CuO 


Hg 2 


HgO 


AgO 


P(0 2 


Sb0 3 




2 


2 


2 


23 


2 


2 


2 


2 


2 




2 


s 


2 


2 






2 




3 


3 






2 


CI 


1 


1 2 


1 


1 


1 


1 


2 


1 


3 




1 


I 


1 


2 


2 


1 






2 


2 


3 






so 3 


1 


2 


1 




1 


1 


1 2 


1 


1 2 


1 


2 


NO <5 


1 


1 






1 


1 


1 


1 


1 


1 




P0 5 


2 


2 








2 


2 


2 


2 






C0 2 


2 


2 






2 


2 


2 


2 


2 






C 2 3 


2 


2 


2 


1 


2 


2 


2 


2 


2 




1 2 


B0 3 


2 


2 


2 




2 


2 


1 










A 


1 


1 


1 


1 


1 


1 


1 2 


1 


1 




1 


T 


2 


2 


1 2 




2 


1 


1 2 


2 


2 




1 


As0. 5 




2 






2 


2 


2 


2 


2 




2 


As0 3 




2 








2 


2 


2 


2 




2 


Cr0 3 


1 


2 


2 




2 


2 


2 


1 2 


2 




2 



the desired information. The numeral 1, indicates solubility in 
water ; 2, solubility in either nitric or hydrochloric acid, and 3, insol- 
ubility in either. The smaller numerals indicate a low degree of 
solubility. 



622 



a r l* K N I) j x 



TABLE X. 

HOMOLOGOUS SERIES OF ORGANIC ACIDS. 



1. Formic C 2 H 2 4 

2. Acetic C 4 H 4 4 

3. Propionic C e H G 4 

4. Butyric C c H 3 4 

5. Valeric C 10 H l0 O 4 

6. Caproic C 12 H lo 4 

7. Enantbylic . . . C l4 H 14 4 

8. Caprylic C l6 H 16 4 

9. Pelargonic. . . . C 18 H ly 4 

10. Capric C 20 H 20 O 4 

11. Margaritic .... C 22 H 2O 4 

12. Laurie C 24 H 24 4 

13. Cocinic C 26 H 20 4 

14. Myristic C 28 H2 8 4 

15. Benic C 30 H 30 4 



16. 
17. 
18. 
19. 
20. 
21. 
22. 
23. 
24. 
25. 
26. 
27. 
28. 
29. 
30. 



Ethalic C 32 H 32 04 

Stearic C 34 H 34 4 

Bassic C 36 H 36 4 

Behenic C 44 H 44 4 

Cerotic C 54 H 54 4 

Melissic C 60 H 60 O 4 



TABLE XI. 

COMPOSITION OF THE ASHES OF COMMON CROPS. 





Indian 
Corn. 


Wheat. 


Wheat 
Straw. 


Eye. 


Oats. 


Pota- 
toes. 


Tur- 
nips. 


Hay. 


Carbonic acid 


trace. 

0.5 

49.2 

0.3 

0.1 

17.5 

23.2 

3.8 

0.8 

0.1 

4.5 


1.0 

47.0 

trace. 

2.9 

15.9 

29.5 

trace. 

1.8 

trace. 

2.4 


1.0 
3.1 
0.6 
8.5 
5.0 
7.2 
0.3 
67.6 
1.0 

5.7 


1.5 
47.3 

2.9 
10.1 

32.8 
4.4 
0.2 
0.8 


10 5 

43.8 

0.3 

4.9 

9.9 

j-27.2 

2.7 
0.4 

0.3 


10.4 
7.1 

11.3 
2.7 
1.8 
5.4 

51.5 

trace. 

86 

0.5 

0.7 


13.6 
7.6 
3.5 

13.6 
5.3 

42.0 
5.2 
7.9 
1.8 


2.7 
6.0 
2.6 

22.9 
57 

18.2 
2.8 

37.9 
1.7 

1C0.C 

1C0O 

to 
2000 


Sulphuric acid 

Phosphoric acid 

Chlorine 

Lime 

Magnesia 

Potash 


Soda 

Silica 


Iron 


Charcoal in ash, { 
and loss, f 


Lbs. of material re- ) 
quired to yield 100 > 
lbs. of ashes. ) 


100.0 
10000 


100.0 
5000 


100.0 
2000 


100.0 
5000 


100.0 
2500 


100.0 

6000 

to 

13000 


100.0 

12500 

to 
20000 



INDEX. 



Absorption of heat, 44. 

Acetates, 513. 

Acid, acetic, 512 ; arsenic, 220 ; 
arsenious, 219 ; boracic, 246 ; car- 
bonic, 235 ; chloric, 181 ; citric, 
518. 

Acid, gallic, 520 ; hydriodic and 
hydrobromic, 270 ; hydrochloric, 
267 ; hydrochloric, action on 
metals, 269; hydrofluoric, 270 ; 
hydrosulphuric, 272 ; hydrosul- 
phuric discolors metals and paints, 
273 ; hydrosulphuric, relations to 
life, 274; malic, 518 ; nitric, 207 ; 
organic, 511; oxalic, 514; pyro- 
gallic, 520; silicic, 244; sul- 
phuric, 193 ; action of on metals, 
199 ; sulphuric, affinity for water, 
199 ; sulphurous, 189 ; tannic, 
518 ; tartaric, 516. 

Acids and bases, 160. 

Acids, formation ofj 159. 

Aerated bread, 546. 

Affinity, 9. 

Agricultural chemistry, 554. 

Air, analysis of, 205. 

Air and vapor, relations of, 79 ; 
capacity for vapor, 80, 87 ; mixed 
currents, 83 ; necessary to all 
animals, 595 ; unsaturated with 
vapor, 82. 

Albumen, 538. 

Alcohol, 497 ; conversion into alde- 
hyde, 507 ; conversion into ether, 
505 ; conversion into vinegar, 
508 ; in spirituous liquors, 618 ; 
in wines, 503 ; methylic, 510. 

Aldehyde, 507. ' 

Ale, 505. 



Alkalies, 380. 

Alkaloids, 524. 

Alloys, 358. 

All substances fusible, 71. 

Altitudes, measurement of) 95. 

Alum, 405. 

Alums, 406. 

Alumina, 387. 

Aluminated plaster, 403. 

Aluminum, 312 ; alloys of, 361. 

Amalgams, — glass mirrors, 342. 

Ambrotypes, 437. 

Ammonia, 274; artificial, 561. 

Ammonium, 308 ; amalgam, 309 ; 
oxide of, 384. 

Analysis of heat, 52. 

Anastatic printing, 438. 

Anchor ice, 65. 

Aniline, 485. 

Animal and vegetable life, 564; 
fluids, 573 ; heat, 591 ; nutrition, 
586 ; solids, 565 ; tissues, change 
of, 596. 

Annealing, 319. 

Anthracite coal, 480. 

Antimony, 329 ; effects of heat and 
air, and chlorine, 330. 

Appendix, 606. 

.Aqua ammoniae, 275. 

Aqua regia, 269. 

Arsenic, 217; antidotes for, 222; 
compounds of, 220, 221; detection 
of, 222; distinguished from anti- 
mony, 225 ; eaters, 228. 

Arseniuretted hydrogen. 220. 

Ashes, composition ofj in common 
crops, 620 ; effect of. on soils, 
559. 

Asphaltum, 480. 



624 



INDEX. 



Atmosphere. 204; elastic force of, 
90 ; weight of, 89. 

Atomic heat, 610 ; theory, 608 ; 
volumes, 610 ; weight and den- 
sity, relations of, 609. 

Atoms, 7 ; combination and weight, 
152 ; contact of, 10. 

Attraction, 9. 

Barium, 310. 

Bell metal, 360. 

Benzole, 484. 

Beer, 505. 

Bile, 580. 

Bismuth, 331 ; effect of heat and air, 

uses of, 332. 
Bitumen, 480. 
Bituminous coal, 479. 
Bleaching, 179, 187. 
Blood, 573; changes in, 589; change 

of color, 592 ; circulation, 587 ; 

composition of, 574 ; composition 

of human, 616. 
Blow-pipe, 289 ; flame, heating by, 

291; flame, oxidizing — reducing, 

290; oxygen, 291; oxyhydrogen, 

292. 
Boilers, incrustations in, 415. 
Boiling, effect of depth, 96 ; effect 

of height, 95 ; effected by latent 

heat, 113; expansion in, 93. 
Boiling point, change of, 96 ; points 

of liquids, 616. 
Bones, 565. 

Borates, borax glass, 427. 
Boron, 246. 
Brass, 359. 
Bread, 544; aerated, 546; making, 

547 ; new and stale, 548. 
Bromides, 396. 
Bromine, 184. 
Bronze, 360. 

Bronzing copper vessels, 335. 
Building in reference to heat, 36. 
Burning fluid, 529. 
Burning glass of ice, 54; glasses, 52. 
Butter, 576. 

Cadmium, 326. 

Calcium, 311; light, 296; oxide of, 
385. 



Camphors, 531. 

Calico printing, 552. 

Caoutchouc, 537. 

Carbon, 228. 

Carbon and hydrogen, 279-285. 

Carbonates, 411. 

Carbonate of ammonia, 413 ; of 
lime, 414 ; of potassa, 412 ; of 
soda, 412. 

Carbonated waters, 237. 

Carbonic acid food for plants and 
poison for animals, 239 ; poison- 
ing, recovery from, 241 ; removed 
from wells, 240 ; solidified, 241. 

Carbonic oxide, 242, 243. 

Casein, 538. 

Cedriret, 478. 

Cells, the lowest form of organiza- 
tion, 461. 

Cement, hydraulic, 387. 

Central fire of the earth, protection 
from, 33. 

Champagne, 503. 

Charcoal fires in close rooms, 241 ; 
ores reduced by, 234 ; prep- 
aration of, 229; properties of, 
231. 

Cheese, 576. 

Chemical attraction, 9; changes in 
the animal body, 588 ; equiva- 
lents, 157 ; rays, 50. 

Chemicals and apparatus for exper- 
iments described in this work, 
629. 

Chlorides, 390. 

Chloride of aluminum, 395 ; of 
lime, 394 ; of sodium or common 
salt, 391. 

Chlorine, 173. 

Chloroform, 509. 

Chromates, 428. 

Chrome, green, orange, yellow, 
429 ; yellow, 552. 

Chromium, 321. 

Circulation of matter, 601. 

Clamps in walls affected by heat, 
60. 

Clay, 419 ; use of, in soils, 556. 

Clothing, 35. 

Cloud-capped mountains, 85. 

Coal, 479 ; distillation of, 483. 



INDEX. 



625 



Coal oils, 483; tar, products of, 484. 

Cobalt, 322. 

Cohesion, 8 ; and affinity, 367. 

Coil and magnet, mutual action, 
144 ; magnetic, 143 ; motion o£ 
142 ; polarity of) 141 ; polarity 
of, imparted to iron, 144. 

Coils, mutual action of, 143. 

Cold denned, 29 ; extreme, how 
measured, 69; radiation of, 50; 
water floats on warmer, 63 ; wa- 
ter, results of its lightness, 63. 

Colloid and crystalloid substances 
separated, 459. 

Collodion, 472. 

Colloid substances, 456. 

Colloids the basis of organization, 
457. 

Color affects absorption of heat, 45 ; 
chauged by heat and by touch, 
397. 

Colored flames, 395. 

Coloring matters, 548. 

Colors, complementary, 24; pri- 
mary, 23 ; various, by the same 
dye, 550. 

Combination favored by solution, 
161 ; influenced by heat, 160. 

Combining measures or volumes, 609. 

Combustible minerals, 479. 

Combustion by nitric acid, 211 ; of; 
phosphorus, 212 ; supported by 
oxygen, 287 ; under water, 215 ; 
without oxygen, 288. 

Composts, 560. 

Conduction of heat, 32. 

Convection of heat, 39 ; made visi- 
ble, 40. 

Cooling of the earth, 48. 

Copper, 332. 

Copying medallions, 188; medals 
and wood cuts, 133. 

Counterfeiting, 439. 

Cryophorus, or frost-bearer, 78. 

Crystallization. 264, 369 ; water of; 
370. 

Crystalloid substances, diffusibility 

ofj 455. 
Crystals, modification of, 373. 
Crystals, systems of, 374; variety 
and forms, 372. 



Culinary paradox, 97. 
Cupellation, 344. 
Cyanide of potassium, 522. 
Cyanogen, 521. 

Daguerreotype, 432. 

Davy's safety lamp, 281. 

Decomposition of a salt, 128 ; of wa- 
ter, 126. 

Definite proportions, 156. 

Deposition of metals, 129. 

Deville and Debray's method of 
preparing platinum, 355. 

Dew, 49, 86. 

Dewpoint, 85. 

Diamagnetism. 120. 

Diamond, 232.' 

Diamonds, value of, 233. 

Digestion, 583. 

Disinfecting properties of sulphur- 
ous acid, 192. 

Distillation, 114 ; of alcohol, 500. 

Dyeing, 549: with logwood, 551; 
with Prussian blue, 551. 

Dyes, mineral, 551. 

Earthenware, 425 

Effervescent drinks, 238. 

Electric current, heating effects, 

134. 
Elastic force of steam, 100. 
Electric light, 134. 
Electrical condition of atoms, 125. 
Electricity, 121; conduction of, 123 ; 

heat from, 31; quantity of, 126; 

theory of, 122; voltaic, 124. 
Electrodes, 125. 
Elementary bodies, 163. 
Elements, 8 ; electrical relation of, 

161 ; number and constitution of 

151: table of, 154. 
Equivalents, chemical, 157. 
Essences, artificial, 532. 
Essential oils, 526. 
Etching on glass, 271. 
Ether from alcohol, 505. 
Ethyl, 506. 
Eupion, 477. 
Evaporation, a protection from heat, 

79; economy in, 114; effect of 

wind, 81. 



626 



INDEX. 



Expansion, by heat, 58 ; of gases, 
65 ; of liquids, 61 ; of solids, 58, 
615 ; universal, 58 ; of water by 
cold, 62 ; of wood and marble, 61. 

Explosions in mines, 281. 

Fats, composition of, 568. 

Fermentation, 541, 543. 

Ferri cyanogen, 523. 

Ferrocyanides, 523. 

Ferrocyanogen, 523. 

Fertility, maintenance of, 562. 

Fibrin, vegetable, 538. 

Filtration, 261. 

Fire by compression, 5*7. 

Fire on w r ater, 39. 

Flame, 286; color of, 296; effect 
of, on metals, 288; non-luminous, 
294; oxidizing and reducing, 
289. 

Flameless lamps, 293. 

Flames colored by chlorides, 395. 

Flesh, 565. 

Flour, 544. 

Fluor spar, 398. 

Fluorides, 398. 

Fluorine, 185. 

Fog and mist, 83 ; vesicular vapor, 
266. 

Fogs of Newfoundland, 85; on 
rivers, 85 ; on the sea-coast, 84. 

Food, preparation of, 584 ; relation 
to temperature, 595 ; respiratory 
and sanguineous constituents, 617. 
varieties of, 598. 

Fracture of glass vessels, 61. 

Fraunhofer's dark lines, 25. 

Freezing by evaporation, 78 ; freez- 
ing point, 14 ; makes latent heat 
sensible, 75 ; mixtures, 73. 

Friction, heat from, 31. 

Fuel, economy of, 242. 

Furs of animals, 36. 

Fusel oil, 510. 

Fusible metals, 360. 

Galvanism, discovery of, 149. 

Gas from wood, 285 ; illuminating, 

283 ; works, 284. 
Gases, law of expansion, 65. 
G^tric juice, 578. 



Gelatine, 567. 

German silver, 359. 

Germination, 460. 

Gilding, 353. 

Glass, 421 ; cut by hot wire, 61 ; 

soluble, 420 ; staining, 389. 
Glazing earthenware, 425. 
Glucose, 496. 
Glycerine, 570. 
Gold, amalgamation, 351; assay, 

352; coin, purity, 353; refining 

process, 350 ; separated from 

lead and copper, 351. 
Groves' battery, 607. 
Gravitation, 8. 
Guano, agricultural value, 560; 

value of, 614. 
Gum, 491 ; elastic, 537 ; resins, 536. 
Gun-cotton, 470 ; powder, 409. 
Gutta-percha, 537. 

Harmless fire, 215. 

Heat, absorption of, 44 ; analysis of 
different rays, 52,- and density, 
relation of, 56 ; animal, 591 ; be- 
comes sensible in freezing, 75; 
change of refrangibility, 54; 
changes effected by, 55 : commu- 
nication of, 32 ; convection of, 39; 
disappearance ofj in vapors, 77; 
disappears in boiling, 94 ; dynam- 
ical theory, 27; in melting, 72; 
effect of different rays in melting 
snow, 53 ; effect on different sub- 
stances, 55 ; extreme, how meas- 
ured, 70; from friction, 31; how 
it expands bodies, 58 ; material 
theory, 27 ; mechanical equivalent 
of, 111 ; nature of, 26 ; of the fixed 
stars, 31; of the sun, 30; protec- 
tion from by evaporation, 79; ra- 
diation of, 42 ; rays and chemical 
rays, 50 ; reflection and absorption, 
47 ; reflection of, 46 ; refraction of, 
50; relative, 56; sensation of, 37; 
sources of, 29; specific, 55, 615; 
theories of, 27 ; transmission of, 
46; walls lifted by, 60. 

Heating, effects of electricity, 134 ; 
rooms, 41 ; the atmosphere, 42 ; 
water, 34. 



D E X. 



627 



Homologous series, 453, 620. 

Hot water pipes expand, 59. 

Hydraulic cement, 387. 

Hydrogen, 247; and carbon. 279; 
compounds, 267 ; gun. 253 ; heavy 
carburet ted, 282 ; light carbu- j 
retted, 279 ; phosphuretted, 277. ' 

Ice, burning glass of. 54 ; effect of, 
on climate. 75 ; formation warms 
cellars, 75; in the tropics, 48. 

Illuminating gas. 283. 

Incandescence, 294. 

Indigo, 548. 

Ink, 519. 

Introduction. 1. 

Introductory, 5. 

Iodides, 396. 

Iodine, 181 ; engravings copied by, 
184: test for, 396. 

Isomerism, 445. 

Isomorphism, 377. 

Iron. 315; as a medicine. 320; by 
hydrogen, 320 ; persulphate. 406. : 

Ivory black, 230. 

Kapnomor, 477. 
Kerosene, 483. 
Kreasote, 476. 

Lampblack, 230. 

Laughing gas, 210. 

Latent heat, quantity of, 113. 

Lead. 335 : action of air and heat, 
336; action of water, 337 ; tree, 
338. 

Lens, 21. 

Lenses, decompose white light, 24. 

Ley den jar. 124. 

Liebig's extract of meat, 586 ; pot- 
ash bulbs, 612. 

Ligaments. 567. 

Light, analysis of, 22 ; calcium, 
296; chemical action of. 11, 434; 
divergence of, 14 ; electric, 134 ; 
is without weight, 11 : laws of, 
14; Newton's theory, 12; ray, 
pencil, beam, and medium of, 
defined, 13 ; reflection of, 16 ; 
the source of vision, 11; undu- 
latory theory, 12. 



Lignite, 479. 

Liniments, 572. 

Liquids non-conductors, 38. 

Lime, 385 ; action on mineral mat- 
ter, 557; action on organic mat- 
ter, 558; ignition by, 386; in 
mortar, 387 ; superphosphate, 563; 
use in soils, 556. 

Liquefaction, 71. 

Logwood, 549. 

Lungs, 589. 

Madder, 549. 

Magnesium — magnesium light, 311. 

Magnet, action of a single wire, 145. 

Magnetic needle, 117 ; properties 
of electric current, 140; tele- 
graph, 147. 

Magnetism, electrical theory of, 
146; induced, 119 ; of steel per- 
manent, 145. 

Magnets, 116 ; attraction for each 
other, 117. 

Manganates, 430. 

Manganese, 314. 

Marble, artificial, 416. 

Matches, 216. 

Matter, circulation of, 601 ; three 
states of; 10. 

Mechanical equivalent of heat, 111. 

Medals, copying, 133. 

Mercury, 339. 

Melting of snow cools the air, 74 ; 
points of solids, 616. 

Metals, 298 : as conductors of heat, 
S3: classification of, 301; depo- 
sition of, 129 ; phvsical properties 
of 299. 

Milk. 575; composition of 617; 
solidified, 577. 

Mineral green. 552 ; oils, 481. 

Miniature fountain, 276. 

Mirrors, concave. 16. 

Mist and fog, 83. 

Moisture, deposition of, 81. 

Mixed currents of air, 83. 

Molasses, 495. 

Monsel's salt, 406. 

Mordants, 549. 

Morphine, 525. 

Muntz's sheathing metal, 359. 



628 



INDEX, 



Muscle, structure of, 566. 
Musical tones by burning hydrogen, 
254. 

Naphtha, 481. 

Naphthalin, 486. 

Nickel, 322. 

Nicotine, 525. 

Nitrates, 407. 

Nitrate of ammonia, 410 ; of lime, 

408 ; of potassa, 408 ; of silver, 

411. 
Nitre, uses of, 409. 
Nutrition of animals, 586. 
Nitrobenzole, 485. 



Ocean a reservoir of heat, 57. 

Oil of apple, of bitter almonds, of 
grapes, of wintergreen, 533 ; of 
bergamot, of pine apple, 532 ; 
vitriol, manufacture, 194. 

Oils composed of carbon and hy- 
drogen, 528 ; containing oxygen, 
531 ; containing sulphur, 532 ; 
empyreumatic, 533 ; volatile or 
essential, 526. 

Olefiant gas from alcohol, 507. 

Opodeldoc, 572. 

Organic bases, 524 ; chemistry, 441 ; 
compounds, change and multipli- 
cation, 447 ; growth, material of, 
443 ; matter, 442 ; products un- 
stable, 443 ; tissues, destruction 
of, 212. 

Orpiment, 220. 

Oxalates, 515. 

Oxidation in animals, 594; of me- 
tals, 208. 

Oxide carbonic, 242. 

Oxides, 378 ; names and formation, 
158. 

Oxide, nitric, 209. 

Oxygen, 163 ; blow-pipe, 291 ; ex- 
periments with, 167. 

Oxyhydrogen, blow-pipe, 292. 

Ozone, 172. 

Pancreatic fluid, 580. 
Paraffin, 478. 
Peat, 478. 



Pepsin, 580. 

Petrifactions, 245. 

Petroleum, 482. 

Pewter, 360. 

Phenic acid, 486. 

Philospher's lamp, 252. 

Phosphates, 416. 

Phosphate of lime, 417. 

Phosphuretted hydrogen, 27 7 

Phosphorescence, 214. 

Phosphorus, 212; red, 216. 

Photographic printing, 437. 

Photography, 431. 

Picamar, 477. 

Picric acid, 486. 

Pittacal, 478. 

Plants, constituents of, 466 ; min- 
eral constituents of, 554 ; motion 
of fluids in, 465 ; relation of, to 
the soil, 554. 

Plaster casts, 402. 

Platinum, 354; condenses gases, 
357 ; Deville and Debray's meth- 
od of preparing, 355. 

Polarity of the coil, 141. 

Porcelain painting,. 42 6. 

Potash, prussiate, 522. 

Potassa, 381 ; action on animal and 
vegetable matter, 383. 

Potassium, 303; combustion in 
carbonic acid, 306 ; combustion 
on water, 305. 

Precipitation, 261, 366. 

Pressure, relation to boiling, 94. 

Primary colors, 23. 

Prism, triangular, 19. 

Proportions, definite, 156; multi- 
ple, 157. 

Protein bodies, 538. 

Prussic acid, 524. 

Putrefaction, 540. 

Radiation of heat, 42. 

Radicles, compound, 450. 

Ratsbane, 219. 

Reflection of light, 16. 

Refraction, 18. 

Refrangibility of heat changed, 

54. 
Refrigerators, 37. 
Resins, 533. 



INDEX. 



629 



Respiration, 589. 
Respired air, changes in, 593. 
Root, office of, 464. 
Rosin oil and gas, 536. 
Rosin soap, 535. 

Safes, fire-proof, 37. 
Safety lamp, 281. 
Safety valve, 105. 

Salads and summer sours, 59 : . 

Sal volatile, 413. 

Saliva, 577. 

Salting meat, 586. 

Salts, 362; basic water in, 371; 
binary theory of, 364; double, 
363 ; formation of, 159 ; names 
of, 158. 

Sand, use in soils, 556. 

Sealing-wax, 536. 

Sea-water, 393. 

Sensation of heat, 37. 

Setting a river on fire, 305. 

Shot and bullets, 338. 

Silica, soluble, 245. 

Silicates, 419. 

Silicon, 244. 

Silver, 343 ; assay ; coin, 347 ; cu- 
pellation of, 344; separated from 
copper ; uses of, 349. 

Silvering apparatus, 130; solution,131. 

Singing of tea-kettle, 99. 

Sizing, 535. 

Smee's Battery, 607. 

Smoke, 230. 

Snow crystals, 264; warmth of, 36. 

Soaps, 571 ; properties of, 572. 

Soda, 384. 

Sodium, 307 ; uses, 308. 

Soils, composition of, 555; exhaust- 
ion of, 561 ; use of vegetable 
matter in, 555; vegetable and 
animal matter in, 555. 

Solar atmosphere, 297. 

Soldering and welding, 427. 

Solders, 360. 

Solids become liquid by heat, 71. 

Soluble glass, 420. 

Solubility in water and acids, 620. 

Solution, 260, 365 ; and chemical 
combination, 369. 

Specific heat. 615. 



Spectra of metals, 296. 

Spectral analysis, 25. 

Spectroscope, 25. 

Speculum metal, 359. 

Stalactites, 415. 

Starch, 487 ; conversion into gum 
and sugar. 490. 

Stars, heat of, 31. 

Starvation, 597. 

Steam boilers, 99 : elastic force of, 
100; engine, 106 ; heating by, 112 ; 
condenser, 109; gauges, 104. 

Stearic acid, 570. 

Steel, 319; writing upon, 320. 

Straw bleaching, 188. 

Strontium, 310. 

Strychnine, 525. 

Substitution compounds, 452. 

Sugar, 493 ; boiling, 98 ; manufac- 
ture, 192. 

Sulphates, 401. 

Sulphate of baryta, 404; of lime, 
402; of soda, 403. 

Sulphur, 186 ; bleaching by, 187. 

Sulphurets, 398. 

Superphosphate of lime, 418, 563. 

Symbols, chemical, 152. 

Taxnixg, 568. 

Tartar, 504. 

Tartaric acid, 516. 

Tartrates, 517. 

Telegraph, magnetic, 147. 

Temperature, measurement of; 66 ; 
equilibrium of, 47; relation to 
pressure, 101. 

Tempering steel, 319. 

Tendons, 567. 

Theine,- 525. 

Thermometer, 66; air, 70; centi- 
grade, 67 ; Fahrenheit's, 68. 

Three states of matter, 10. 

Tin, 326; action of acids on, 327; 
coating pins, 328; crystalline, 
329 ; ornamenting with," 328. 

Tin- ware, 329. 

Type metal, 360. 

Types of organic compounds, 450. 

Urea, 596, 



630 



INDEX, 



Vaporization, 76. 

Yapor and air, relations of, 79; 
quantity in the atmosphere, 80, 
82; vesicular, 266. 

Vapors, conversion into liquids, 112 ; 
density, elasticity, formation, 
transparent, 76 ; disappearance 
of heat, 77; several kinds may 
occupy the same space, 88. 

Varnishes, 534. 

Vegetable albumen and casein, 538 ; 
chemistry, 460 ; fibrin, 538 ; jelly, 
492; nutrition, 463; parchment, 
469; 

Vinegar, 512; deterioration, 513; 
from alcohol, 508. 

Vitriols, 407. 

Volatile oils, 526. 

Voltaic batteries, 138. 

Voltaic battery, Smee's — Groves', 
607 ; current, force of, 607 ; 
electricity, 124; electricity, physi- 
ological effects, 149; electricity, 
source and chemical action, 136 ; 
pile, 139. 

Vulcanized rubber, 537. 



Water, chemical combinations of, 
264; composition of, 256: de- 
composition of, 126 ; hammer, 
98 ; hard and soft, 263 ; of crys- 
tallization, 370; purity of, 262; 
relations of, to life, 265. 

Welding iron, 318. 

Wheel tires, rivets, &c, 59. 

Wind affects evaporation, 81. 

Wines, 5 03-; alcohol in, 503 ; flavor 
of, 504; preserving, 191. 

Wood, action of reagents on, 467 
charred by sulphuric acid, 199 
converted into sugar, 468 ; cuts, 
copying, 133 ; prevention of de- 
cay, 474; spirit, 475; tar, 477 
vinegar, 476. 

Woody fiber, 467 ; fiber, decay of, 
473 ; fiber, effect of heat, 475. 

Writing on steel, 320. 

Yeast, 541; powders, 545. 

Zero, absolute, 69. 
Zinc, 323. 



APPENDIX. 



631 



LIST OF CHEMICALS AND APPARATUS REQUIRED FOR THE EXPERI- 
MENTS DESCRIBED IN THIS WORK 



1. 


lb. 


Black Oxide of Manganese. 


1 oz. Block Tin. 


1 


u 


Bleaching Powders. 


1 " Bismuth. 


I 


H 


Chlorate of Potassa. 


2 ls Mercury, (Quicksilver.) 


1 

4 


11 


Alum. 


1 " Arsenious Acid, (Ratsbane.) 


i 


u 


Sulphur. 


\ " Tartar Emetic. 


i 


(( 


Common Caustic Potash, in 


\ " Iodide of Potassium. 






Sticks. 


\ u Iodine. 


i 


u 


Acetate of Lead, (Sugar of 


{ " Potassium. 






Lead.) 


| " Solution of Chloride of Plati- 


1 


II 


Sulphate of Copper, (Blue 


num. 






Yitriol.) 


1 Glass (4 oz.) Spirit Lamp. 


I 


it 


Carbonate of Ammonia, (Sal 


Fine Platinum Foil and Wire. 






Volatile.) 


1 doz. assorted Test-tubes. 


2 


OZ 


Bichromate of Potash. 


J Sheet blue Litmus Paper. 


2 


II 


Bone Black. 


J " red Litmus Paper. 


2 


II 


Sulphuret of Iron. 


Fine Iron Wire. 


2 


II 


Nitrate of Potash, (Saltpetre.) 


* Sheet Zinc. 


1 


II 


Chloride of Ammonium, (Sal 


* Sheet Copper. 






Ammoniac.) 


* Sulphuric Acid, (Oil of Yitriol.) 


1 


a 


Yellow Prussiate of Potash. 


* Hydrochloric Acid, (Muriatic 


1 


u 


Cyanide of Potassium. 


Acid.) 


1 


ii 


Oxalic Acid. 


* Nitric Acid, (aqua fortis.) 


1 


n 


Ground Nut Galls. 


* Alcohol. 


1 


ii 


Phosphorus. 


* Ether. 


1 


u 


Fluor Spar. 


* Clay Pipes and Vials. 


1 


ii 


Borax. 


* Bowls, Tumblers, &c. 


1 


ii 


Chloride of Barium. 


* 1 yard small India Rubber Tube. 


1 


ii 


Chloride of Strontium. 


* Small Glass Tubes. 


1 


ii 


Beeswax. 


* 1 Small "Wedgewood Mortar. 


1 


ii 


Chloride of Mercury, (Corro- 


* 1 Iron Tripod. 






sive Sublimate.) 


* 1 Spirit Lamp. 


1 


ii 


Metallic Antimony. 


* 1 Small Bell Glass. 



* Not contained in the box of apparatus and materials put up to accompany this 
work. ^ 




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